the dorbel daily

Backwoods v zyxtcba Part 3

2012-02-10T02:37:00.001-08:00

It's Game Six now and zyxtcba (Black) has built a comfortable 6-2 lead. It's Backwoods (White) who is on roll here though, with one of those juicy late game positions so volatile that the cube is red hot on almost every roll.

Position One

The pipcount favours Black 75-105, but that shouldn't stop White from doubling here. Hit and dance is a market loser and he has lots of rolls that hit two checkers. He can actually be too good after this next sequence. Black has the stronger board of course and that 30 pip lead, so he can take. White's play isn't always straightforward though and after the take he rolled 2-1, playing 17-14*. This is not a big error, but the double hit is clearly right. Always do what the enemy does not want you to do. If you were playing Black here, do you want White to put two men on the roof? Emphatically not. The double hit clearly wins more gammons and trailing 2-6 Black has to select that option. Anyway, he played 17/14*, Black rolled 2-6 and we got to this position.

Position Two

White only has one number that misses and here it is, 5-5. Worse still, he crucially misplays it with 15/5, 14/9, 6/1. The best play is 14/4, 9/4(2), leaving a checker on the 15pt to cover the outfield as best it can. There was no more hitting after this and in the end White staggered over the line and won the race.

Game Seven started with Black now leading 6-4 to 13. There were no interesting cube opportunities for either side in this game, but there were two checker plays that clearly illuminate themes that recur over and over again, so it will be valuable to look at these.

Position Three. Black leads 6-4 to 13 and has to play a 6-4.

What's your play?

Later in the same game, it's White on roll. Black is on the bar.

Position 4

White correctly decided that he was now too good to double and rolled 6-1. What's your play?

We'll take a look at these tomorrow. Until then, enjoy the game!

Backwoods v. zyxtcba Part 2.

2012-02-08T01:20:00.000-08:00

We pick up the match in Game Four, with Backwoods (White) leading 2-1.

Neither side has had a correct double up until now, but White is on roll here after Black (zyxtcba) has just run off his 20pt anchor with a 6-5.

Posi

White leads 72-79 and I think most of us will recognise this as a double. Backwoods certainly did and turned the cube. Can Black take? You do need to have a methodology for race doubles, as they occur often and guesswork will lead to a lot of mistakes in commonplace positions. The simplest, which works well enough for a straightforward race like this is 8-9-12. Compare your pipcount to the opponent. If you lead by 8% you have enough for an initial double. If you lead by 9% you have a redouble and if you lead by 12%, then that is the first point at which the opponent should correctly pass. Here Black leads by 7 in a 72 pip race. 7/72 is 10% approximately, a clear double and a straightforward take. Do not worry about the fact that Black needs five cross-overs to White's three. Crossovers do matter, but not very much and they can usually be safely ignored. White's stack on the 6pt and gap on the 5pt would also be taken into account by perfectionists, but just knowing the length of the race and the size of the lead gives us the correct answer, double/take. Those of you who want to refine your racing cube play can search the Internet for Walter Trice's Rule 62, The Keith Count, The Ward Count and others!

In Position One, Black only wins about 23% of the games if they are played out to the end cubeless, but owning the cube in a race with a lot of mileage left has enough value to give Black a take and later on we got down to this delightful position with Black on roll.

Position Two

What's the correct cube action for both sides? In very short races like this, with only a few checkers left and uneven distribution, just using 8-9-12 is often misleading, but it actually gets this one right. Black leads by 2 pips with 16 to go and 2/16 is 12.5% indicating double/pass, which is the right answer! We can also look at this as a three roll position, i.e. one where both sides are likely to be off in three rolls. TIP. An equal three roll position is double/pass.
That is to say that if White's position was the mirror image of Black's, it's double and pass so clearly White must drop here where he is worse than that.
As above, you can further refine your technique in these short races with unequal distribution with one of the counting methods mentioned above. I would add to this the Thorp formula, old and easy to use, but for most of us, keeping it simple is good!

White blundered and took and so went into game Five trailing 2-5 to 13. Black built a strong position and arrived at this next position on roll.

Position Three

Any time that you have a five prime with an enemy checker behind it, you have to think about doubling, if only because to see a cube in this position is not what White wants! Always do what the other player does not want you to do. White emphatically doesn't want to be doubled, so it's a cube. Perhaps Black is inclined to be cautious because he is the match leader and feels that that is his best strategy. Perhaps he think that if things go well he might win a gammon, we don't know. At all events he didn't double, White breathed a sigh of relief and the next exchange (Black 6-1, 24/17*, White 5-3, bar/22, 13/8* got us to Position Four.

Position Four

Don't you just hate to double from the bar? Join the club, but when there are blots to be hit and you have a five prime with two enemy checkers behind it, it is right and actually Position 4 is a marginal take/pass. TIP. A 22 pt anchor behind a five prime is usually a pass. Here, even though Black is on the bar a double is correct with 15 hitting numbers to get among White's three blots. Even if Black dances, White will still be struggling to tidy up and note that awkward stack on the 6pt too. A doubling opportunity missed and next turn Black had a big cash after hitting from the bar.

Zyxtcba's victory in the play-off's at the end of Fibs League season 54 was just sufficient to propel him into the top 12 in the Master's list for 2011. These players now go into a knock-out contest to decide the supreme champion for the year. All ties are best-of-three 9 point matches. The first round features the players who finished in the 5th to 12th spots. An all-German tie matches BushSucks with masselkopp, Mason_Verger (Germany) plays zyxtcba (California, USA), roadkillbooks (Argentina) plays otto (Canada) and Schigolch (Germany) plays mano (France). The winners of these ties will advance to the quarter-finals, where the seeded players, jarma (Hawaii, USA), dorbel (UK), BluNick (Italy) and PHunter (Switzerland) wait for them. 12 players from 8 countries demonstrates the wide appeal of this excellent league, smoothly run for us by Tomawaky, so if you don't play in it and want some good action, sign up today at Fibsleague .

Until tomorrow, enjoy the game!

Fibs League 54 Play-off

2012-02-06T07:56:00.001-08:00

In my last post I promised you some riveting "defending against a back-game" stuff. The game turned out to be even more difficult than I thought, with very long rollouts needed and a lot of thinking time, so rather than present you with something half-baked and not thought out, I'll postpone that for a bit.
Not much use trying to explain it to you if I don't know what's going on in the first place!

Instead, some reporting. Fibsleague, Franck del Rio's long running contest reached the end of session 54 with a 13 pt play-off between zyxtcba (USA) and Backwoods (Finland). Zyx had never won the title, while BW was going for his record setting sixth crown and was the favourite in most eyes. Zyxtcba was the winner in a thriller, 13-12 so let's take a look at some of the major decisions.

Game 1. 0-0 to 13. White (Backwoods) on roll.

White has caught Black cold and put two checkers on the bar and correctly doubles this. Can Black take it? Zyxtcba passed and you can hardly blame him. Nobody likes to take with two men on the bar, but it's a fairly clear take and the pass is a blunder. What are the features that might lead us to the right decision? White only has a two point board as yet and still has only eight checkers in the zone. The midpoint is still stacked and the back checkers haven't moved. The point that White has made is the 3pt, useful but not a killer and the point that White has slotted is the 2pt, not ideal.
How can we add all this up and get "take" at the end? If only there was some nice formula that took all these factors into account, but that is the Holy Grail of backgammon theorists. Keep this one in mind next time you get caught out by an early blitz. Improvements for White, a better point made, a better point slotted, split back checkers, another builder in the outfield, any of these can push this one into the drop box.

One of the biggest equity sinks for all of us is the missed double. There are a number of reasons for this. First and foremost, doubling any position gives your opponent the chance to make a mistake, passing when he should take or vice versa. Also, if taken you can't then make subsequent missed double mistakes! A string of four or five missed doubles hurts a lot. A third subtle feature is that most players below expert level handle redoubles poorly, often missing a chance for a correct 4 cube. Handing the cube to an opponent of this type eliminates your chance of a doubling error and opens the opportunity for your opponent to make a big mistake or two.

Game 2. Black 0 White 1 to 13. Black on roll.

Zyxtcba (Black) misses a chance to double here. He has a small lead (128-136), he has escaped his back checkers and his front position should develop nicely, giving him winning chances racing, priming or even blitzing in some variations. White can still take. His own front position is OK, so if he can hit a shot he can turn it round quickly and he might jump out and win the race too. Nevertheless, Black should double this and let White have a problem, even though he probably knows that White, a bold taker and redoubler, will make good use of the cube if he can.
Black missed two more chances to double this one before eventually cashing to level the scores.

Game 3. 1-1 to 13. White on roll.

Backwoods (White) missed a very rare doubling opportunity here. Usually doubling while you are still anchored like this is a no-no, race lead (127-148) or not. Here though Black is going to have a lot of difficulty unloading that grossly obese midpoint and building a board. White's plan is to run the blot off the 20pt and then wait for a double or a 5-x to clear his anchor. After that, the race should be easy to win. I can't see that I would have doubled here either though. I am just being wise after the event.
In the match Backwoods ran the blot with a 6-2, zyxtcba eschewed the hit after rolling 2-1 and we got to this position.

Game 3. 1-1 to 13. White on roll.

Here's why it was correct for White to double last turn. He has escaped his blot and gained in the race and this is now a pass! This is really exactly the same as when you double with the midpoint to clear against a bar anchor. White has plenty of time to roll the double that does the job and should only face one single shot when he doesn't. In the match he again chose to roll and rolled a 5-5 for mega market loss. Two very unusual positions and we'll go on and look at Game Four tomorrow. I do mean tomorrow I promise.
Until then, enjoy the game!

More Golden Point Stuff

2012-01-31T06:11:00.000-08:00

In the last post we looked at a couple of difficult plays, where the player had an option to make his 5pt or hit. Here's the first.

Black leads 2-0 to 5. He chose to play 24/18*, but Timothy Chow in his comment pointed out all the downside to that play. Too many return shots, a staggering 30 (!), after which White may well make her bar anyway. Four blots is also more than most positions can stand when you are outboarded also. What we have to grasp here is that this is highly likely to develop into a prime/prime struggle and for that, you need a prime. 10/4 makes a very useful point and leaves no blots, but it also makes it very hard for Black to make his bar and his 5pt in the time that he has left. The best play, by a lot, is 10/5, 6/5 and leave the 4pt slotted. Anything else is a blunder. After that play, White is a favourite to make her bar or hit, but is unlikely to do both. If she hits, Black will get return shots. If she makes the prime, Black will be a favourite to make a four point board.
Making the 5pt is a world class play. Not sure I would have spotted it. I think that I would have made the 4pt, wrongly.

In this position, trailing 4-away, 3-away, Black decided to double. A doubled gammon takes him nicely to the winning post, while cube ownership and gammons are much less useful than usual for White. It's a pretty easy take and technically it's a bit short of being a double too, but I still like it. Black won't have to make any more doubling decisions and if he gets lucky he can win this match in a few rolls. A useful guide incidentally, although not infallible, is "Never double until you've made a point inboard". This is still known in London as the Dimitri Rule, after Dimitri Kourdoulas the likeable Cypriot regular at the old Double Five Club.
After doubling, Black had to play 4-1 and opted for the double hit, 8/4*/3*. This of course leaves Black with six (!) blots and no hiding place if White gets among them. XG2 will play this at all levels up to ++, but a 2592 game rollout was unable to separate the two plays. They are essentially equal. I like making the 5pt. Rather as in the first position, it gives you a position with which you can fight the upcoming battle. It also unstacks the 6pt and leaves Black nicely placed to blitz or make a five prime, or both. It also looks to me as if it will be fairly easy to play. Still, if like Paul Weaver and XG2 you like the double hit, go for it! Acording to the rollout you will do as well as me, provided you can handle the complex game that has to follow.

Tomorrow I want to look at some positions where I was trying to defend against a backgame. In the later stages, the plays are usually fairly regular, but in the first stages immediately after the Big Bang as it were, the plays are far from obvious. How well does the bot play them? How well did I play them? We'll see, but until then, enjoy the game!

The Golden Point.

2012-01-28T07:23:00.000-08:00

Just how important is it to make the 5pt? Often we are presented with a choice of making it or using the roll to hit somewhere else. In a different form we also sometimes have the opportunity to make either Golden Point. There are of course no definitive answers. Sometimes it's right and sometimes it's wrong, but today we can have a look at a range of positions, some commonplace, some rare.

Here's a very common one and most of you know this one.

Position One.

It's always correct to hit, money or match, any score. Hitting gains 20 pips in the race and removes the White slot. Still, many intermediate and beginner players still make their 5pt with this one, wrongly. How about with 1-1? Now making the bar and 5pts is correct and hitting is always wrong, although not by a great deal at some scores.
That was an easy one, so how about this?

Position Two

Not many people run out with 5-4 or 6-3, so you don't often see this one, but against weak players it can be a good alternate if they don't know how to play 3-1.
Hitting is clearly correct and making the 5pt is an error. What you do with the one is not so clear. I always hit and split, but 13/10*/9 is also quite good.

Much more commonplace is the response when White has made a major split.

Position Three

For money and at GammonSave, making the 5pt figures to be correct, but at GammonGo and DMP the issue is far from clearcut. I haven't rolled this out (although I will) but at lower levels of evaluation (XG2++) there is nothing to choose between them. A very common mistake here is to make the 4pt with a 4-2, but hitting is correct except at GammonSave where the two plays are very close.

Now let's move on to some more difficult stuff. Here's a position that a student faced and got wrong. What would you have done with this?

Position Four

Leading 2-0 to 5 Black had this 5-1 to play. Hit? Make the 5pt? Make the 4pt? And if you think that one is hard, try this one!

Position Five

Here Black, the renowned American expert Paul Weaver, is trailing 4-away, 3-away to Mochy.
As an extra problem, should he double this? If he does and gets a take, how should he play a 4-1?

Take your time, you have a day, possibly two to think about this one! If anybody has actually rolled out Position Three I'd like to hear from you.
Until the next time, enjoy the game!

Advertising.

2012-01-27T10:53:00.000-08:00

I'm sorry that you haven't had much to look at these last few days. Sometimes inspiration dries up, sometimes I research some positions and then find that in fact they are not as interesting as I first thought, sometimes I write something and then find that even I am falling asleep while reading it! However, enthusiasm is welling up again and I have some nice themes to look at this week. Hit or make the 5 point, an ever-recurring problem, some ways of looking at race cubes for beginners and how to make the most out of playing against bots. That's all in the next few days while I sit around with my leg up after having my varicose veins stripped (recommended for masochists and anaesthesia fans).
In the meantime, I want all of my British readers to mark a date in their diaries, for the annual Scope Charity tournament at the RAC Club on 26th February. This is a superbly run (Mike Main and Peter Bennet) day out in a fabulous venue, with a champagne reception, the best brunch you will ever eat, auctions and of course backgammon. It benefits Scope, the Cerebral Palsy charity and you will have a terrific day out and may even win something. More details at this url .

My annotated matches are still available at $10 a go.
Mochy v Falafel, 13pts. The two best players in the world playing at world champion level.
Mochy v Melzi, 13pts. Mochy takes on Carlo Melzi, the world class Italian.
Mochy v Peever, 13pts, Mochy v Paul Weaver, the world class American teacher.

All the significant plays rolled out and interesting positions annotated by me, with some comments from Mochy. Specify XG, Gnu, Snowie or Word doc.
payPal to dorbel(at)gmail(dot)com.

Finally, personal lessons are always available for all levels below expert. Based on your actual matches and focussing on the areas that lose you the most equity, these are only 20 euros a lesson. Think they might suit you? Ask for a free trial!

Finally, the best online league is Fibs League . Join anytime and usually start straight away. Well run, good fun, recommended.

That's it for today, tomorrow I hope to have something for you that isn't advertising! Until then, enjoy the game!

Last Man Standing and Friends.

2012-01-15T03:27:00.001-08:00

Here we are again, money game, Black on roll holds the cube, White with 14 checkers off is still dancing. Can Black redouble?

Not unless he wants to be beavered! White is a small favourite here and will love to get her hands on the cube in this immensely volatile position. Basically Black isn't yet in a four roll position, as 24 of his rolls only bear one man off. He still has some danger of leaving a shot too. The same number of checkers on three points is no redouble and a take and even if you move them all down to the lowest two (or one) points, White can easily take a correct redouble.

When Black gets down to six checkers though things are very different.

Now 18 rolls bear off two or more checkers and White's chances of dancing and getting a shot are of course dramatically reduced. Now Black should redouble and White should pass, usually with a small sigh. It's awful to lose with 14 men off. We've gone from no double/beaver to redouble/pass in a roll, an indicator of the huge volatility when one side (or both) is down to a single checker. White can take if she has entered and reached her 18pt. That position looks like this.

While White was on the bar, the position was complicated by the chances of her dancing again and/or getting a shot but now that it is just a race we can use EPC to figure this out. Her task in running round is of course simple, but she will sometimes enter her home board with a roll that doesn't bear off usually meaning last roll wastage. For that reason, we have to add some pips to her pipcount and the agreed figure for a single checker is 3.5, so her EPC is 21.5. Black is a little worse than a true three roll position, as not all his doubles save a roll and he may yet roll three consecutive ones. Quite arbitrarily I add 0.5 of a pip to that to make his EPC 22.5, so redouble/take.
If you don't know what EPC is then you need to read this article.
Walter Trice invented this and it is very valuable. He expands upon this further in his articles in GammonVillage Magazine .

It is premium content, so you will need a subscription, very good value at $50 a year, huge archive of articles and matches, with new content added regularly. You could also buy Walter's wonnderful book, "Backgammon Boot Camp", arguably the most bangs for your buck on the market.

Until the next time, enjoy the game!

Last Man Standing.

2012-01-12T02:44:00.000-08:00

In the Christmas Quiz I emphasised the difficulty facing the player whose opponent has taken off 14 men. There are unusual checker plays that you have to make, but today I just want to look at using the cube.

Here's a position that you might face. Black hit White's's last man and closed her out and White has danced every time up to here. It's a money game, so what's the correct cube action for both sides?

Black didn't double and rolled 6-5, taking two off and White danced again leaving the position below.

Now what's the correct cube action for both sides?

I'll expand on this tomorrow, so if you want a comment, get it in now!

Enjoy the game!

The Answers Part Two

2012-01-10T06:30:00.001-08:00

The answers for Numbers 6 to 10

Position 6

Money game, Black to play 3-3.
The plays that include 5/2*(2) do very badly in the rollout. Switching from priming to blitzing when you have already cubed and you don't have the ammo in position for the attack just isn't the plan. That solid 7 to 4 block is Black's big asset and shouldn't be traded away. Rather surprisingly Bill Davis and Danny Kleinman liked bar/22, 13/10, 5/2*(2) back in 1990 and so did Barclay Cooke when he showed the position as No 102 in Paradoxes and Probabilities. That's a shockingly bad play and so is hitting twice! So, what's best? It's probably one of these, either bar/22, 21/18*/15, 13/10 or bar/22, 24/18*, 13/10. The rollout hasn't split them yet. If it does I'll let you know and for now I'll allow either as the winner. Two entrants got the first of these.

Position 7.

Money game, Black to play 5-1.
All good quizes need a position like this. The answer is of course 7/2, 7/6, for minimum shots and to avoid the 6-6 disaster next when not hit.
Two entrants got this right.

Position 8.

Make the play of 6-6 that leaves the fewest shots.
Dead sneaky this one. The answer is 14/2, 10/4(2). This appears to leave 11 shots, but actually only leaves 5. You have to play the full roll if you can, so White can't hit with 6-1, 4-1 or 2-1!
Only one entrant got this right and he was honest enough to say that he had seen it before and remembered the trick.

Position 9

Money game, Black to play 1-1.

2/off(2), More wins, more gammons, more backgammons. It does leave a big mess after rolling a 1 next turn, but for that to hurt you have to roll a 1, get hit, hit back and then get hit. That's 30% x 30% x 30% x 55% = somewhere between 1 and 2% and even then you haven't lost as you own the cube. Gumpi also cleverly points out that playing 2/1(4) creates 2-1 as a blot number next turn. Only one entrant got this one right.

Position 10

Money game, Black to play 5-3.
24/21, 9/4. When you have to leave a blot, or as here blots, put them where they will do most good if not hit. This play at least puts the blots on points that Black really wants. 11/8, 9/4 is the only alternate that comes close on XG++ but I admit that I haven't rolled this one out yet. Our experts from 1990 also picked this play and 3 of the class of 2012 also nailed it.

So after all that, who won? Stiefnu scored a brilliant 7/10 just squeezing in ahead of Timothy Chow who totalled an excellent 6. Well done all of you and thank you very much for taking part. This blog is nothing without you. If Steve sends me his address I'll send him his wonderful prize, which I just know he will treasure.

Until the next time, enjoy the game!

The Big Quiz, the Answers

2012-01-03T06:14:00.000-08:00

The Answers!

Position One.

Black leads 6-2 to 9. Should he redouble? If he does, should White take?
These positions are very difficult to sort out over the board, as they take us into regions where we are not used to calculating winning chances. For money this is such a monster pass that we don't need to figure White's chances, as they fall so far short of the usual take point. At this score though, a Black redouble puts the match on the line. Let's do our risk/gain analysis.
For Black, ND/WIN is Crawford, needs 7 or 91%.
D/WIN wins the match, 100%
ND/LOSE is needs 3, needs 5 or 65%
D/Lose loses the match, 0%
If Black doubles he risks 65 to gain 9, R/R+G = 65/74 = 88%.
Black's doubling window opens at 88%. Does he have that? It's easier to count White's winners than Black's. White wins when Black fails to throw 2-2 or better (31/36) and then rolls 4-4 or better (3/36). That's 3/36 x 31/36 = 93/1296 or about 7.2%. There's also a sequence when Black rolls 2-1 twice and White bears off in one or two rolls which adds about 0.1%, so we'll give White 7.3% wins and Black 92.7%. The double is clear then and as White can preserve 9% of ME by passing, she should drop. Double/Pass.
6 out of 8 contestants got this right.

Position 2.

Money game, Black to play 3-1.
By the slimmest of margins, 12/9, 11/10 is correct. Dave Kettler and Julia both explained this one very nicely for me, pointing out that 11/7 or 12/8 both waste pips after a specific roll next turn. After 11/7 you waste a pip with 3-2. After 12/8 you waste a pip with a 3-1.
4 out of 8 got this right.

Position 3.

Double match point, Black to play 1-1.
Very tough. A 2592 game rollout plumps for 10/9, 7/6, 3/1*. The answer in 1990 was 10/8, 5/4, 2/1* but the bot places that third 0.015ppg behind. The second place play only 0.004 behind is 7/6, 5/4, 3/1*. Perhaps the biggest surprise for me was that 10/7, 2/1* was only sixth best although still quite close. I assume that this is because if White enters with a 6-1, Black will actually do better to have two men sent back! Also, if White dances, Black doesn't really want his next 6 to be played to the ace point, so plays that leave the outfield spare further back do well. Black really must try to pick up all three checkers if he possibly can.
Nobody got this right, with the majority wanting to make the bar.

Position 4.

7 point match, White leads 5-2, cube action?

Double and take for money, but here no. Cube actions that take our opponent exactly to the winning post are usually suspect and this is no double/take.
Black no double/win, trails 4-away, 2-away. 33%
Black double/win, trails 3-away, 2-away. 40%
Black no double/lose, trails 5-away/Crawford. 16%
Black double/lose, loses match. 0%.
Black is risking 16% to gain 7%, R/R+G = 16/23 = 69.5%
Black needs 69.5% minimum to cube and with only 23 winners and 13 losers he only has just under 64%.
4 out of 8 got this right.

Position 5.

Money game, Black to play 1-1.
It's 2/off(2)! In 1990 they got this one wrong and a 5184 game rollout on XG proves it . Basically the safe play wins almost 100% with 99.31 gammons and 17.08 backgammons. Taking 2 off still wins 97% and although the gammons drop to 62%, backgammons jump to 53%. The difference is only 0.007 of a point and I don't think that there is any way to calculate this over the board, but you may like to consider that a considerable part of White's equity after Black takes off 2 checkers resides in White's ability to use the cube correctly. XG manages this very nicely but how confident are you that you know when to redouble against a man who has born off 14 checkers? It's pretty tough. In practice this should make the 2/off play clearly right.
5 out of 8 got this right.
Tomorrow (really!) I'll post the answers for positions 6 through 10.
After these five, Timothy Chow leads with an excellent 4/5.
Enjoy the game!

A Reader Asks.....

2011-12-30T03:08:00.000-08:00

While we wait for the super computer at Dorbel HQ to process the millions of entries received for the Christmas Quiz, here's an interesting query from a reader trying out XG2 for the first time.
"I'm analysing a three point match, it's 1-1 and the analysis says that White should double here, even though she is an underdog in the game. Why is this?"

This is of course our old friend the 2-away, 2-away scoreline, which everybody claims to understand, yet so few below the expert level do. It is, so the experts say, always correct to double at the first opportunity. So, when White started this game with 3-2 and (correctly) played 24/21, 13/11, Black had an optional double, even though he was a very slight underdog. He should do this because he has nothing to lose by doubling. If he refrains from doubling, White will on her turn double anyway and Black will still have a take.
In the position above, XG says that White should double from the bar. This is because even if White dances, Black should double and White should still take! So, White can't lose by doubling, but what can she gain? If she rolls 4-4 and makes the best play, which is bar/17*, 21/17, 13/9 (not an easy play to find!) and Black rolls 6-6, White has actually lost her market and Black should pass!
If you play below expert level (98% of players), then doubling immediately at this score figures to be right for you. Occasionally it will be a minute mistake, of the order of 0.002 points, but not doing it risks making a much bigger mistake later, so turn it at the first legal opportunity. If you are an expert and playing somebody much weaker than yourself, you can get some mileage from delaying it in the hope of an incorrect pass later or occasionally even playing on until the end for an undoubled gammon! Don't try this at home kids! Trust me, at 2-away, 2-away, turn the cube immediately, even if your opponent starts with a 3-1. It's always correct.
Until the next time, enjoy the game!

The Big Christmas Quiz, Part Two

2011-12-24T09:32:00.000-08:00

Welcome to Part two of the quiz, five more positions hacked from The Chicago Point of May 1990, with grateful thanks to Bill Davis, who co-authored the the original quiz and kindly gave me permission to reproduce it.

Position Six. Black to play 3-3 from the bar. Money game.

Position Seven. Black to play 5-1. Money Game.

Position 8. Black to play 6-6. Make the play that leaves White the fewest shots.

Position Nine. Money Game, Black to play 1-1.

Position 10. Black to play 5-3, money game.

Answers in the comments section please. Go back to Part One if you haven't already done so. Mr Chow please change your answer for Number Four as I have corrected the score so that White leads, not Black.
There is a small but rare prize for the winner and I will post the answers on or about the 28th of this month.
Enjoy the game and for those who celebrate it in one way or another, Happy Christmas!

The Big Christmas Quiz. Part One.

2011-12-22T03:28:00.000-08:00

It's Christmas Quiz Time. Let me say straight away that I didn't compose this quiz. I have lifted it straight out of the May 1990 edition of Chicago Point. It was compiled by Bill Davis and Danny Kleinman and given at the 1990 Midwest Championships, for a $25 entry fee. A stellar list of entrants was topped by Jake Jacobs who scored 6 out of 10, so we may assume that this is a tough quiz! They were restricted to 20 minutes, you can have as long as you like. There will be a prize!

Thank you to Chicago Point , then as now a prime source of backgammon information and it's editor Bill Davis, whose contribution to our wonderful game over all these years is incalculable.

In every position, Black is on roll. You can assume that you are playing an equally strong opponent to yourself. Five positions today, five tomorrow.

Position One. It's a 9 point match and Black holding the cube leads White 6-2. What's the correct cube action for both sides?

Position Two. Money game, Black to play 3-1.

Position Three. It's DMP, how should Black play his 1-1?

Position Four. It's a 7 point match, White leads 5-2 What's the correct cube action for both sides?

Position Five, money game, Black to play 1-1.

An interesting feature of this quiz is that it was composed at a time when bots were in their infancy. The best available was Tom Johnston's Expert Backgammon, a weakling compared to today's heavyweights but a remarkable program for it's time, particularly considering that it was the work of one man. In their answers Bill declared that only positions 6 and 10 were at all debatable, but ExtremeGammon has something to say about that, as we will see. Nevertheless, kudos to both men for an excellent quiz.
Post your answers to these five in the comments section please and I'll put up the next five tomorrow.
Oh yes, what is the prize? The winner will receive a backgammon book! Don't get too excited, it's minute and almost valueless, but it is very old and very cute and will look well on your trophy shelf.
Enjoy the game!

Play The Game Not The Player?

2011-12-20T00:17:00.000-08:00

One of the difficulties facing every backgammon writer is the necessity to qualify every assertion with phrases like "except when" and "if you are the stronger/weaker player" and "depending on the score". There are many others. In order to make what we write intelligible, we have to omit these and rely on the reader to use his/her commonsense to imagine that these qualifiers are permanently in place. Here are some examples.
Recently I wrote, "The best modern players double like the bots do, aiming to turn the cube at the first moment that it is technically correct." I could, perhaps should, have qualified this with "when they are playing against somebody of their own class". As a reader commented, "Stick doesn't do this. He definitely changes his cube play to adjust to the strength and perceived playing habits of his opponent". Of course he does, but I would expect him when playing another world class player to get that cube across pretty much in line with what the bot suggests is correct. Another reader commented on Stick's criticism of people who "play like donkies" and cash positions that are actually too good. Recently Falafel commented on a cube, "I'm not sure if this is a take, but when in doubt I take". Is this good advice for all of us? The point I am trying to get across is this. Is what the bots do invariably and what the stars do some of the time against some players, good for us to follow? Given our more limited skill set, clearly it isn't. Let's take a look at some actual positions.

Position 1

Black trails 6-away, 2-away. What is the correct cube action? This is a monster pass, nobody takes this, so Black's first consideration must be, "Is it too good?" It's not clear to me that it is. White has a five point board and leads in the race by 15 pips. She might hit a fly shot next turn or improve with 1-1 or 2-2 or if hit, anchor on the 22pt. Over the board I would say to myself, "I think this might be too good, but I'm not absolutely sure, so I'll double." Stick might say, "I think this might be too good, although I'm not absolutely sure, so I'll play on for the gammon this roll".
Who is right? We both are. His judgment of the position will be better than mine, both now and on later rolls when he faces the same question. Furthermore, he is likely to play from here better than me, so approaching or even achieving the theoretical equity of the position. For my part (and probably yours) doubling is a good practical play, putting a point on the scoresheet without having to play at all! The actual equity of this is about 1.05 points for Black if he plays on, so the theoretical cost of cashing now is 1/20th of a point. To me this is a reasonable price to pay to get a point that requires no luck, skill or effort from me before it goes on the scoresheet. Also, as so memorably put by Bill Robertie, occasionally somebody hallucinates and takes, after which your equity goes through the roof. One of these pays for 15 games where you have made a small error and cashed.

What about early and aggressive doubling? Take a look at this.

Position 2

Black is on roll in the first game of a 13pt match. He leads by 4 pips. Is this a double? Black is Falafel, White is Mochy and Black doubles. Black threatens to lose his market with the sequence "make the 3pt, White dance". If this doesn't work, he might be able to keep White primed or just race. In the worst sequences, his bar point anchor will keep him in the game for a while yet. By a tiny margin a double is correct, gaining 0.007 points over waiting! Should we copy Falafel and the bot? Sure, why not? Be aggressive, up the ante now and with any luck you'll grab an early 4 point lead in the match. 20% of the games end with a Black gammon from here. Also, as in the first position, doubling allows your opponent the chance to make a big mistake and pass. Not very likely? I've seen weaker cubes than this passed, though not perhaps by Mochy!

What about "When in doubt, take"?

Position 3

Money game, Black on roll, leading by 37 pips. The cube is pretty clear. What about the take? White has an anchor and a good board, is that enough? I can't say for sure that this is a take and because I usually tend to be too optimistic, I pass this. Falafel on the other hand might well say, "Not sure, so I take". For him, this is a good plan. With his superior checker play he will play close to perfectly from here and get the maximum benefit from cube ownership. Black only has to make one error to make the take correct and in fact the theoretical equity of this position after a take is 1.042. For me and perhaps for you too, a pass costing 1/25th of a point is a good practical option.

Every player can and should consider the practical benefits of adjusting his cube actions to allow for his own and his opponent's strengths. I hope that this article will give you some clues as to what you should be aiming for. Theoretical bot perfection isn't always the best practical option over the board, sometimes yes as in position 2, sometimes no as in positions 1 and 3.
Enjoy this wonderful game!

If Early Is Good, How Early Is Early?

2011-12-19T01:43:00.000-08:00

Gallon Jug describes players on Play65, presumably in money games, doubling as soon as the game starts and appearing to do very well by doing so. What is actually happening here? We can start by looking back at a favourite hustler's proposition from the old days when they were lucky enough to hook a fish. "I tell you what", he would say, "I'll let you have 1-1 as the opening roll every game. However, we have to start with me owning the cube on 2." On roll in this position, the hustler is only around 42% to win the game, but he is hoping that his better play and most importantly his cube ownership will pull him up to being a small favourite. Cube ownership is so valuable for two reasons. Firstly if things go the way of the fish, the hustler will stay in the game until the end. Fish has to get to 100% to claim the points. Hustler however, only has to get to around 75% to turn an optimal cube to 4. He has only to climb from 42% to 75%, whereas Fish has to climb from 58% to 100%, a longer ladder. Secondly, the greater part of the Fish's wins will come at the two level, but a lot of the Hustler's wins will be at the 4 level.
What about Play65? Well if players at all levels below world class are reluctant doublers, which I believe to be true, they are even more reluctant redoublers, so cube ownership for them is less valuable than it is for the Hustler in our example above. Moreover, Play65 is a money site and they make their money by taking 10% of every settled game. The player who wins pays this. Thus if at the end of a game at a dollar a point, you win $2 you collect $1-80. This has a very considerable effect on your take point. Normally as you know you need 25% cubeless to have a marginal take, but on a site with a 10% rake, you need 26.32%. It gets worse too. GJ doesn't say so, but the site allows you to cap the amount that you can lose in any one game. If it is capped at twice the stake, then they will double at any advantage at all. Why not if cube ownership is valueless? If on the other hand you don't follow this policy and wait for a more normal doubling point, you lose equity on each turn. If the game is capped at 4 times the stake, the player owning the cube at 2 should redouble immediately they become the favourite, particularly as it is easier than usual to lose your market anyway. If they do this and you don't, they gain.
Of course if they see that you are as aware of these wrinkles as them and can also play the checkers fairly well, they quickly move on to look for other fish. The key skill in any money game is to select your opponent carefully.
Can you make money on a site with a rake as high as 10%? Yes, if you are prepared to be completely ruthless, can play very well and concentrate very hard for hours at a stretch. Ideally you cheat as well by using a computer. Wouldn't the site monitor the games and close the account of anybody doing this? No, why would they? They don't want to ban a player who plays for long periods every day, because they get their money whoever wins the game. Occasionally a cheat will be outed by the other players, but not by the site itself.
Enjoy the game and by all means play for money, but at a 10% rake, I can't advise it to anybody.
Until tomorrow, have fun!

Lastgamephobia II: The Sequel

2011-12-16T13:49:00.000-08:00

Those of you who read the comments will have seen Timothy Chow's comment on the last post. I reproduce it here for those who didn't. Thanks Timothy, but I fundamentally disagree with you. Here's why.

"There is one reason you may not want to double at 4a2a as aggressively as the bot says you should. A lot of positions that the bot drops at this score will be easy money takes and therefore will be taken by many players. If your opponent is likely to take next turn even though it is technically a drop, then you can't actually lose your market."

This is worth looking at more closely. The examples that I gave are not early doubles in the sense that they are technically wrong, they are correct doubles and to wait a turn loses equity. If we wait until there has been a market losing sequence and yet our opponent incorrectly takes, we don't gain anything. It's the same game with the cube in the same place as it would have been when we doubled correctly earlier. In order to reach that point we have to make one or more cube errors and then rely on our opponent to make a mistake in order to avoid losing equity by losing our market!
Lastgamephobia afflicts both doublers and takers. If you open with a 3-1 and the opponent rolls a lemon, 6-3 say, then believe me you can and do get wrong passes by correctly doubling immediately. At this score, lastgamephobia sufferers also get sudden attacks of gammonphobia. You can't gain by missing a correct double at this score, only lose.

Traditional cube play technique was to try and double as close to the point where a take becomes a pass as possible. There are several drawbacks to this.
First, it requires very precise judgment to identify when you have reached this point and balance it against market losers. Doubling at the first correct point is a lot easier to spot, because you only need to be in the ballpark.
Second, you almost always have to miss several correct doubles to get to that point. Doubling early means that you might make a mistake when you double, but it will be the only one that you make in that game.
Thirdly, if you double at what was traditionally considered the optimum point, i.e. at the place where you gain a theoretical point by getting a take or an actual point when the opponent passes, it isn't then possible for the opponent to make a mistake! She loses a point either way. Doubling early allows her to make a big mistake by wrongly passing.

The bots, who play better than humans 24/7, double early. The very best players and there are a few who consider a PR in excess of 2 to be playing badly, double like the bots do. We have nothing to lose and everything to gain by trying to emulate them. In the process, we will certainly make matches shorter, but dont be afraid of that. It's a game of aggression. Make aggressive doubles and reap the rewards.
Enjoy the game!

Lastgamephobia

2011-12-16T00:39:00.000-08:00

The player reaching 4-away, 2-away in a match can use the cube with a great deal of freedom, as the cube turn kills the cube and the opponent's gammons and activates his own gammons as match winners. This statement is so obvious to strong players that you often see them doubling on their second roll of the game.

Here's a typical position with Black trailing 4-away, 2-away and on roll. He leads by a pip, has already made a point and White has three blots, a recipe for a strong cube at this score but most intermediates and many advanced players will leave the cube in the middle here. The intermediates as a group are reluctant doublers at the best of times and they routinely miss doubling opportunities. The advanced players know intellectually that they ought to be doubling but they fall victim to a crippling malady which I call Lastgamephobia. They don't want to put the match on the line, even though they know that they should.
If you too don't like to double this position and many like it, think of it as a money game, where your opponent is not allowed to recube and she is not allowed to win a gammon but she can lose one! Why wait? How can you gain? By cashing a point and going to 3-away, 2-away?
Black often gets these chances on his second turn and White usually has a take, although yesterday I saw the sequence Black 3-1, White 6-3 doubled and passed by somebody I would call a strong player.

Lastgamephobia strikes in many ways. On the same day I saw this redouble passed in the first game of a three point match.

Actually Black, perhaps also suffering from the dread disease, had already missed two cast iron opportunities to turn the cube to 4 and put the match on the line, but when he turned it here, White passed. She elected to play at Crawford needs 3, with a Match Equity of 25% rather than take her 30% chance of winning the match from here.
Can you justify White's decision if she is the stronger player? Yes, if White thinks that she is good enough to win 56% (or better) of one point matches against a player of Black's strength, then she might be right to pass. This is though very hard to estimate. Ratings vary so widely that they are not much help as a guide and there is also the fact that if you poll players after matches, 70% of them think that they were the stronger player!
The same principle applies all through our matches. Double early, double often. Better to make one small mistake with a cube that is a bit frisky than make a string of mistakes failing to double your opponent in and then cashing when you are too good, a sequence that you can see day in, day out anywhere the game is played. Be bold and above all, don't be afraid to make this game the last one if it is right to do so. I know two players on Fibs of roughly equal strength with the checkers; in tournaments and fibsleague I play both of them fairly regularly. One is a dashing cube handler, who turns the cube with boldness and isn't afraid to redouble aggressively too. The other is reluctant to double until he is very close to or actually past the point where it is a pass and never, ever recubes unless it is a pass. One beats me often, the other almost never does so. Guess which is which?
Enjoy the game!

More On "A Reader Asks..."

2011-12-14T04:06:00.000-08:00

Timothy Chow has helpfully pointed out that Neil Kazaross recently updated his famous "Neil's Numbers" chart and for that you need to go to this.
That was a very exciting moment for me. I just worked out how to make a hyper-link!
Will I be learning the new values? I might, but the benefit of from doing so is very small, as the real problem in most cases is putting a sufficiently accurate figure on the position in the first place! The best method for getting to grips with the one above is to learn how to operate Walter Trice's Effective Pip Count. I could write it all out for you but best if you just go here.
The EPC won't entirely answer the position above for you, because it doesn't allow for White dancing and it doesn't include her chances of hitting a shot later. However, what it does do is to provide you with a method for comparing a home board with a home board and a straggler, when the actual pipcount is more or less meaningless. It's the AK-47 of the bg world. You won't often need it, but when you do, nothing else is half as comforting!
The promised 4-away, 2-away positions are in the pipeline and I may even write them later today, but for now, cooking lunch for mrs dorbel is more important.
However, I will take this opportunity to remind you of the annotated matches that I have for sale. The first is;
Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.
Every important move analysed and commented on by me, with the approval of and some comments from both players. These are arguably the two best players inthe world right now.
The second is ;
Mochizuki Masayuki v. Carlo Melzi, a 13pt IIBGF Match.
Annotated as above.
Please order from dorbel(at)gmail(dot)com, $10 for either match. The file is ideal for Extremegammon, but please say if you use Gnu or Snowie and I will send you a suitable file.

Work in progress, Mochy v. Paul Weaver. A 13pt IIBGF match.

Until the next time, enjoy the game!

A Reader Asks........

2011-12-12T05:20:00.001-08:00

"Why shouldn't I redouble this position?" writes A Nonnymouse of South Africa. "I'm a huge favourite in the position and I lead 8/2 to 11, so White can't win the match after a redouble, yet Gnu marks my redouble as an error."

The first thing to say about this is that Gnu 2-ply is not very good at assessing this type of position. It does mark this as a substantial error, but the rollout marks this is being a very marginal double/no double, with Black winning the match about 93.25% whether he doubles or not. As White might pass, I suppose that doubling figures to be correct, because a pass will take Black to Crawford - needs 9 where his equity will be about 94.5% according to the MET that I use. If Black is the weaker player he should definitely cube, as the position is entirely skill free.
Extreme Gammon agrees with these figures.
So, don't ever take a bot evaluation as gospel. Always check it if you are interested in the position.

Nr Nonnymouse got it right. This is just about a redouble and a correct take, but I would imagine that many players would be very reluctant to turn the cube here and risk an 8 point loss when they can only win 3. Black is actually a 90% favourite to win here, so how would one arrive at the correct decision over the board? We do a risk/gain analysis.
Note that for this, I round all percentages down to the nearest whole number to make the arithmetic easier and I assume when I say "Black no double" that he never doubles. In practice he will do a bit better than this figure if he redoubles correctly later. Of course White always redoubles to 8 immediately.

If Black doesn't redouble and wins, he gets to Crawford - needs 9, ME= 94%
If Black redoubles and wins, he wins the match, ME = 100%
We can see that Black stands to gain 6% by doubling.
If Black doesn't redouble and loses, he gets to needs 3 - needs 7, ME = 76%
If Black redoubles and loses, he gets to needs 3 - Crawford, ME = 25%
We can see that Black risks losing 51% by doubling.

So, Risk/ Risk + Gain = 51/51 + 6 = 51/57 or 89.5%.
Balck needs to be a 90% favourite to redouble and that is almost what he has.

Can you do this in your head over the board? Very strong players can. It depends on being able to put a very exact figure on Black's game wiining chances, which in itself is very hard and then being able to remember your Match Equity Table.
Memorising Match Equity Tables is very hard for anybody. Kit Woolsey says that he can't even remember his own, although I am sure that he knows all the figures for shorter matches. For this reason, most players rely on an approximation and the most popular is Neil's Numbers.

It looks like this.
The leader's percent probability of winning the match is 50, plus the number of points by which he leads multiplied by Neil's number. Look at the top line to see how many points the trailer needs and the appropriate Neil's Number is underneath it. Some of the numbers don't have a whole number, so you have to fill that in for yourself. As originally designed, the user was intended to extrapolate, so for example the number for trailer needs 7 would be 6.5.

This handy gadget was designed by Neil Kazaross about 20 years ago ans is startlingly accurate even when compared to today's computer generated tables. However, don't use it when the leader only needs one or two points to win as it breaks down there, but these lines are quite easy to learn anyway.

One can of course use pencil and paper when playing online which helps and also have a printout of a match equity table to hand. Don't do this when playing a human. It isn't fair and it is cheating and you will feel very sneaky after doing it. However, if you do use a pencil and paper for your calculation when playing a bot, you will be learning how to do it until the day when you can do it mentally. The small fraction of a rating point that you might gain by this doesn't matter much, if at all!

Tomorrow, I want to look at some 4-away, 2-away positions. Until then, enjoy the game!

The Sharp End Answers

2011-11-30T06:30:00.000-08:00

If you haven't seen the previous post, entitled The Sharp End, go there first for the problems.

Let's take a look at them.

Position One

Black (me) trails 3-away, 2-away. Sometimes position are much simpler than they appear. Black trails in the race 72-104 before the roll and although White's count is not as good as it looks, with the gap on the 4pt and the stack on the 1pt, that's still a substantial lead. When I first started playing tournaments, which was within a few weeks of playing my first ever game, I felt very intimidated. My opponents would sometimes study a position for an age before making their play. Often on my turn I had no idea what the best play was and no idea how to figure it out either, so I used to do the one thing that I could do in order to look as if I was actually a deep thinker like them. I counted the pips. After a while, I began to realise that the pipcount often indicated the right play! It does here too. Black trails in the race and must stay back as far as possible and block as many rolls as possible. 9/2 is the play, although in the match I actually cleared the 8pt. I was worried about having two blots in board if I got a shot and hit it, but that is jumping at shadows. If I don't get a shot, or I do and miss it, I have two points slotted. If I do hit a shot only 6-4 is enough of a lemon to fail to cover one of them. Stay back, block points, build a board as fast as you can, all point to the best play, 9/2. 2/3 for the panel.

Position 2

Position 1 wasn't even tough when looked at closely. This one is. It is of course the next play in the game, but now things have changed radically. One feature of the last position was that White would only be forced to leave a shot with some sixes, but now all the fives (except 5-5) leave a shot too, so plays like 9/3, 5/1 or the panel's choice of 9/3, 6/2 are less palatable. You have to volunteer a shot with 9/5, 9/3.
When White hits and you dance, you are of course sad, but you aren't dead yet and besides, that sequence only occurs 12/36 x 16/36 or about 14%. The rest of the time you are very glad indeed to have the 5pt. 86 glads and 14 sads is a good ratio. 0/3 for the panel.

Position 3

Different match, this position is double match point, that is, any position where the cube is dead and if either side wins the game, they win the match.
In Position One, we saw that aggressive slotting worked well when the opponent was still unlikely to leave a shot immediately and in position two, we saw that 5pt ownership was essential. Both of those guidelines work well here too. I'm not sure what the best play is, but it's one of these. 6/5, 4/2 or 4/1 or 3/1, 2/1! Whichever of these you choose, you can see that either the 5 or 6pts is slotted, essential for Black if there is going to be hitting. The Panel scored 2/3 here.

Position 4

I love this one. All the panel voted to keep the shots down with 14/8, 14/10, but it's right to play 13/3! Why volunteer 4 extra shots? To generate a double hit after 6/5, 6/3, 6/2 and 6/1. It's just about worth it.

Position 5

Not too hard. Black trails 3-away, 2-away, although that is not very important. It's all about volatility with 15 numbers to make the 2pt on White's head and another 17 to hit loose. I doubled this and rolled 6-3 after White correctly took.
Here's a handy tip to quickly calculate the number of rolls that make the 2pt. It's the square of the direct hitters, minus any non working doubles. Here that's 4 squared = 16, minus 5-5 which doesn't work. Saves a lot of work. All our intrepid panel doubled this and only one wasn't sure of the clear take. Thanks to them for their efforts, thanks to you for reading. Until the next time, enjoy the game!

The Sharp End

2011-11-28T07:57:00.000-08:00

These are some problems I encountered recently, all coming at the sharp end of the game where there is still a lot of contact and truck loads of equity are at stake on every roll. The first two are from a match I played. Black is on roll, trailing 6-7 to 9. What's your play?

Position One

The second best play is a double blunder, so be careful.

Position Two

And this is the next roll, another opportunity to make a double blunder. What's your play?

The very next day I had a match to analyse for a student and these two positions reminded me of the two we have just seen.

Position 3

It's double match point, so what is Black's play. You can't make a big mistake here, but it's good to get it right and know what you are trying to do, because it's dmp and the wrong play can cost you two wins in a hundred.

Position 4

Same game, next turn. Again, you can't make a big mistake but it is dmp, so even a small mistake can lose you one game in a hundred. What and why please.

Lastly, the bastard child of Positions 1 and 2. I got down to this, trailing 3-away, 2-away. Black on roll. Is it a cube? If it is, is it a take?

Position 5

Fun for all the family! If you get all these right, my hat is off to you. If you know why you are doing it, then you are either Stick Rice or God, certainly a better man than me in either case!

Until we come back to these, enjoy the game!

Answers

2011-11-28T02:09:00.001-08:00

These are the answers to the last post, so please go back to "Keeping An Eye On The Masters" if you haven't seen it already.

Black to play 6-1. Mochy played bar/24, 13/7 to keep his anchor, leave fewer shots and bid for a prime of his own.
The cost of this is of course that being hit costs 18 pips and allows White to leave his anchor with a tempo, but by a small margin it is the best play. Bar/18 is a small error.

Should White double this? By a hairsbreadth, this is not quite a double technically, but as a double would in theory cost you 11 thousandths of a point (after a 1296 game rollout), it is in my view worth a punt! It's pretty volatile. If White is a much weaker player than Mochy (as 99.99% of players are) then I think that she should double this and hope to get lucky. Here, White is Paul Weaver, a world class player in his own right, so he reasons that handing a very takeable cube to a man who is arguably the best player in the world is not a good plan!

Now White is on roll. The correct cube action for Black is not hard to find. It's an enormous pass. Is White too good to double? By a small margin he is and doubling is an error costing 0.054 of a point. However, a double is, in my view, a good practical play. Although White has an equity of 1.054 points if he plays on, that is theoretical and he will have to play well to get it. When he doubles he puts a solid point onto the scoresheet without even having to roll, much less play. To me, 1/20th of a point is a reasonable price to pay for that.
All of these positions are from Game One of a 13 pointer between Mochizuki Masayuki and Paul Weaver and this match will soon be available as an annotated file.

In my next post, which will be later today if the Good Lord's willing and the creek's don't rise, I have four ultra tough checker plays for you, all from the sharp end of the game when there are huge amounts of equity riding on every roll. You'll love 'em so stay tuned.
Until then, enjoy the game!

Keeping An Eye On The Masters

2011-11-25T13:16:00.000-08:00

On GridGammon I've had the pleasure of watching two superbly played matches between Mochy from Japan and Paul Weaver of the US. I am annotating these and hopefully they will be available in a couple of weeks for students. To whet your appetite here are some cute positions from Match One, Game One.

Position One

Mochy (Black) to play 6-1 from the bar. What should he play?

He played bar/24, 13/7, leaving Paul Weaver White on roll in position 2 below.

Position 2

Should White double?

In the match, he elected to roll and rolled 3-3, correctly playing 24/18*(2). Mochy entered with 4-1 played bar/24, 6/2, probably right, leaving White on roll again in position 3 below.

Position 3

Should White double and if he does, should Black take?

Find out tomorrow! Comments welcome as always. Until then, enjoy the game.

Starting Out

2011-11-22T06:36:00.000-08:00

It's important to get each game going with a good play. All the old text books had advice on what the best plays were and the arrival on the scene of Jellyfish, Snowie and Gnu meant that keen students could check the accuracy of ideas on the opening plays by playing the starting position over and over again until there was an answer that lay within the program's margin of error. The latest bot, Extreme Gammon 2, is by common consent the most powerful yet and it incorporates a "book" of opening plays and some replies that is the closest yet to being definitive. For your convenience I reproduce a table below of the plays that XG will make on the opening, all of which have been exhaustively tested by a high level rollout.
There are four columns, the first is the correct play for money and for all practical purposes you can assume that this is also the best "normal" play for early in a match, when scores are level or very close. The second column is the best opening at Double Match Point and you can also use this column for Post-Crawford 2-away and 2-away, 2-away games, where the game is very likely to be cubeless and gammon free. The third column is Gammon Save, to be used in the Crawford game when it is important to avoid a gammon, i.e. Crawford, 2-away, 4-away etc.
You can usually use this column when leading towards the end of a long match and in any short match too. The last column is GammonGo, to be used in the Crawford game when it is important to win a gammon, e.g. 2-away, Crawford, 4-away, Crawford etc. You can usually also use this column when trailing towards the end of a long match or in a short one.
You can of course print this page off and use it to cheat, but I hope that you won't do that. Keep it by you and check after you have made your play. That way you will soon learn it.

Opening	$	Dmp	GS	GG
65	24/13	24/13	24/13	24/13
64	24/18, 13/9	24/14	24/14	8/2, 6/2
63	24/18, 13/10	24/18, 13/10	24/18, 13/10	24/18, 13/10
62	24/18, 13/11	24/18, 13/11	24/18, 13/11	13/5
61	13/7, 8/7	13/7, 8/7	13/7, 8/7	13/7, 8/7
54	24/20, 13/8	24/20, 13/8	24/20, 13/8	13/8, 13/9
53	8/3, 6/3	8/3, 6/3	8/3, 6/3	8/3, 6/3
52	24/22, 13/8	24/22, 13/8	24/22, 13/8	13/8, 13/11
51	24/23, 13/8	24/23, 13/8	24/23, 13/8	13/8, 6/5
43	13/10, 13/9	24/21, 13/9	24/21, 13/9	13/10, 13/9
42	8/4, 6/4	8/4, 6/4	8/4, 6/4	8/4, 6/4
41	24/23, 13/9	13/9, 6/5	24/23, 13/9	13/9, 6/5
32	24/21, 13/11	24/21, 13/11	24/21, 13/11	13/10, 13/11
31	8/5, 6/5	8/5, 6/5	8/5, 6/5	8/5, 6/5
21	13/11, 6/5	13/11, 6/5	13/11, 6/5	13/11, 6/5

Some of these plays have very close alternates and for one of them, 64, don't use the money column in match play. At the start of a 3pt match, play 24/14, while for 5pts or more, play 8/2, 6/2. These are not big differences, a few thousandths of a point, but I mention this before somebody else does!

Tip of the Week. The simplest way to improve is to allow yourself a little more thinking time on tough plays. The simplest way to achieve this when faced with a roll where the play is not immediately obvious, is to let go of the mouse while you think! Try it.

One of the fastest and most interesting ways to improve is to study the matches of the best players, particularly when annotated to explain why a play is good (or bad). I have two annotated matches for sale, featuring Mochizuki Masayuki, the 2010 World Champion. They are annotated by me with the approval of and some comments by Mochy. Each is $10 and comes as an XG or Gnu file, with commentary based on XG analysis. For those who prefer to read the plays and use a real board, it also comes as a word document with many colour diagrams for $15 and this includes the XG file.
Mochy v. Falafel, 13pts
Mochy v. Carlo Melzi, 13 pts.
Orders and PayPal to me please at dorbel(at)gmail(dot)com.

Tomorrow a look at some aggressive cube actions when trailing. Until then, enjoy the game!

Back With A Blunder

2011-11-10T03:09:00.000-08:00

Quite a gap since my last post, as my ancient computer took a week off and went on holiday. It's back now, looking relaxed and tanned, but on its return I took the opportunity to give my own game a much needed overhaul. Like the great majority of players, I miss a lot of doubling opportunities. I would go as far as to say that it is the worst single mistake that humans make. I have been concentrating on getting that cube over earlier, even if it means sometimes doubling too early. Better that than missing a double.

So here are a few interesting positions from a recent match against a world class opponent.
White is leading 2-0 to 5 here and I am on roll. This looks like a good number, what would you do with it?

The first thing to note here is that this a correct double (and take) before I rolled the 6-1!
So what did you want to do with it? I went for 8/2*/1, a blunder. 18/17*, 11/5 is better but best of all is 18/17*/11.
Is this obvious? Now I know the right answer I understand what's going on! Two points; firstly 18/17* costs White 17 pips, compared to 2 after 8/2*/1, secondly leaving the blot on the ace point is actually safer than covering it. Count those shots. Even without these two obvious signposts to the correct way forward, a comparison of the two sides shows quite clearly that Black has a strong positional advantage. He has the deadly 6-5-4pts block and he still has the midpoint and all his checkers are in play. White has the less than deadly 3-2-1pts block which equates to 7 checkers out of play and her midpoint is long gone. What all this means in practice is that Black needs to be playing strategically, rather than going for the tactical option of making the 1pt. (In backgammon, tactical means hitting).

Later on in the same game, after some fairly lively exchanges, we got down to this next position, with me on roll and the cube of course still in the middle. Cube action?

The point I need to make here, is that if I had doubled the first position, I wouldn't have a cube decision to make now, even if, as I thought at the time, it was too early! Doubling means that you can only make one doubling error in the game. Leaving the cube in the middle means that you can make a mistake later and sometimes a whole string of them.
Pretty clearly if Black doubles here he will cash. Nobody takes this. A very useful rule is that if you are in the air against a four point board and your opponent is shooting at a second blot, give it up. It's almost always a pass and usually a correct double. Here though Black has a chance to pick up two blots and that's enough to push this position into the "too good to double" bracket.
I'm sorry to say that I cashed this, a blunder, but note that it is a blunder I couldn't have made if I had correctly doubled position 1. This is the hidden benefit to early cubing. It keeps doubling errors down to a maximum of one per game.

In the next game, with White leading 2-1 to 5, she came on roll in this position and made an excellent double.

If you can't see this as a double, particularly when leading, it is the two Black checkers out of play on the ace that are my weakness. You really do need 15 checkers to play with, as White has. It's a fairly comfortable take though, as White's gammons only win three points and the cube is very useful for Black, as if it is turned to 4, he can use all the points. However the key feature is this. A lot of Black's equity lies in his cube ownership and if he isn't going to make good use of it, he should probably pass.

At this score (White 3-away, Black 4-away) White can pass a 4 cube and still retain 40% of the Match Equity at 3-away, 2-away. It follows that Black should be pretty aggressive with the recube and his doubling window actually opens at around 30%! White failed to jump my prime and bust her own with a 5-5, so we came down to this.

It's not often that you get the chance to recube with two men still on the roof, but I reasoned, "I have to throw two sixes and so does she, but I get first go". I recubed. It's a small error. I can lose my market here by throwing a 6 when she doesn't, but it's just as likely that I don't and she does or that we both do, in which case I will be very sad. Better to wait one turn even though I am in the window. Then if neither of us rolls a 6, she has to play and burn one or both of those useful outfield checkers. Then I'll have a correct cube and of course she should take. Note this feature where Black keeps his prime when he dances, but White has to keep playing and busts her board when she can't roll a six.

I learned a lot from looking closely at these decisions and I hope that you did too. With any luck, I'll have something else for you tomorrow, so until, enjoy the game!

Three On The Ace

2011-10-26T01:36:00.000-07:00

The least useful place to have a spare is on your anchor and as the 24pt is the weakest anchor, it follows that having three checkers on it is very bad. It's practically an invitation to the cube, so should Black, who is on the bar double this? If Black doubles, should White take? It's the first game of a five point match and Black did double this and White (dorbel) passed. Give it some thought and then read on.

If you thought that Black is actually too good to double then I would say that that is a reasonable view, given that White already has three back and three more blots are waiting to be hoovered up. OTB I thought that might just be the case and so passed very quickly. To my surprise, this is a correct take. What is happening here? To find that out, you have to revert to the only technique that we had before bots, the hand rollout. In the old days, this involved hours, sometimes days, of playing the position over and over again, ideally with a friend, often alone! There were some techniques for reducing the dice variation, notably changing the opening roll each time, but the number of games that you could complete and the inevitable playing errors made the results of little value in determining the most likely outcome. However, it did give you some practice and a little confidence when you met something like it in the future. We can still do this now, but using the "Play from here" feature on the bot. It will set the pieces up, play one side and tell you afterwards how you played too, allowing you to improve your play in the position as you go on. You can swap sides.
I did this with this position and discovered several things. The first is that because of his awkward position, Black's play is far from straightforward, so in order to achieve anything close to the bot cubeful equity of around 0.9 he will have to play brilliantly. The second is that the position White fears, where she finds herself in an ace point game with several checkers behind a prime just doesn't happen! When she isn't hit, her blots become slots and builders. When she has one or two checkers sent back, she still has lots of play because Black only has a two point board and can't develop it quickly because of his awkward position. All this is not to say that Black is not hot in this game, he will win about 62% from here including 33 gammons, but White does have a take and must seize the chance to play a long difficult game owning the cube. This is particularly true at this score, where the recube can come earlier than usual.

As so often happens, I quickly saw something very like it again.

Also in the first game of a five pointer, but as you can see with several features that improve Black's game. He isn't on the bar and White is, one of his back men has escaped and his forward checkers, although still stacked, are a bit better placed for an attack. I would have passed this, correctly, but Black decided to play on for the gammon. It's quite a reasonable view to take, as he can usually cash later if he wants to, but double/pass is correct. I always repeat a little mantra here, culled from early reading. I think it's Robertie. "The side playing on for an undoubled gammon against an ace point game is either making a mistake or has already made one". This is a very valuable piece of information, although there are scores where playing on is clearly correct, usually when an undoubled gammon wins the game for you.
At the risk of repeating myself to my regular readers (Sid and Doris Bonkers of Neasden), my philosophy is to only play on for the gammon when I am certain that it is correct. When it's a close decision but playing on is correct, this sometimes costs me a small piece of theoretical equity, but it does put a real point onto the scoresheet without having to play to get it. Also, the icing on the cake, sometimes they take!

So, the next time you see a position and you ask yourself, "What is going on here?", play it. You'll learn a lot more from it than you will reading books, or indeed this column.
Until the next time, enjoy the game!

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.
Mochizuki Masayuki v. Carlo Melzi, a 13pt IIBGF Match.

The XG files for these matches, annotated by me and approved by Mochy are now available, $10 each. Gnu and Snowie users can have a Gnu file with the commentary on a separate word doc. Both matches show brilliant play at the highest level and are very instructive for students at all levels.

PayPal please and enquiries to dorbel(at)gmail(dot)com.

Three Puzzle Answers

2011-10-24T01:16:00.000-07:00

Well done to the panel of three bold enough to give us their thoughts on the positions in the last post. The question as to when it is right to slot your own bar is often difficult and I find that it is much influenced by recent events. If I analyse a match where slotting the bar is right and I have missed it, I'm on the lookout for it in the next match and then slot when I shouldn't!

This was our first position, but it came in the next match after I had seen positions two and three, so I was unduly influenced in favour of boldly slotting the bar and leaving 25 shots. 13/9, only 17 shots is a lot better. 6/2 only leaves 16 shots but that checker isn't very useful. Note that the checker on the 9pt is either a slot for that point or a builder, very useful.

Position Two gave us three 4s to play after entering. 8/4(2) is pretty clear and the last 4 is 11/7, giving a double shot, but it's a good point to fight for and it does duplicate 4s and 2s on the other side. It does leave 21 shots though and so I went for the miserable 6/2 which only leaves 17. This dumping play is often wrong, but right just often enough to make it an attractive play when we have been hit a lot in the recent past! Again note the bar point's dual slot/builder function.

Position Three again had Black to enter from the bar and seeing that Black was in the lead, I decided to race it, bar/23, 21/15. This is actually much the hardest of the three positions, so you won't be surprised to hear that I got this one wrong too. 13/7 is easily the best play, unstacking the midpoint and slotting a very valuable point. It is counter-intuitive to risk another man back when you lead in the race, but this bold play has several things going for it. Again, it is a dual slot/builder whereas the 15 pt is neither. It unstacks the midpoint and in doing so applies some pressure on White to tidy up her three blots. Handily it duplicates fours as well.

Not perhaps the world's most exciting positions, but our panel only scored 6/9 so not so easy either. The lesson is to clear your mind of past history, the last match, the last game, even the last move, because past short term experience is a poor guide. A clear mind is a better environment to find the right answer than a cluttered roomful of unwanted baggage.

I've got a student match to look at now and no doubt that will throw up something interesting for us to look at. It's a rare match that doesn't. Until later then, enjoy the game!

Three Puzzles

2011-10-21T05:04:00.001-07:00

There's a great temptation when writing about bg to highlight extremely rare positions where the right play is an elegant and counter-intuitive gem. As the chances of ever seeing anything like it again are vanishingly small, we don't add much to our store of knowledge, although I suppose anything that leads to our viewing backgammon as a never-ending series of puzzles is a good thing. Here's three fairly ordinary looking positions. How would you approach these? They are all from a five point match. In the first it's no score and Black has to play a 4-3.

In Position 2, Black leads 3-away, 5-away and has to play 4-4 from the bar.

Finally, same score and Black is on the bar again with a 6-2 to play.

There's no particular trick to these, but they do have a common theme. Well they have two things in common actually, I butchered all of these as Black!

Let me have your thoughts please and I'll discuss them in full in the next post.

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.
Mochizuki Masayuki v. Carlo Melzi, a 13pt IIBGF Match.

PayPal please and enquiries to dorbel(at)gmail(dot)com.

Until tomorrow, enjoy the game!

The Famous Five Find The Answers.

2011-10-15T01:16:00.000-07:00

The "Famous Five" were the heroes of a series of British children's books written by Enid Blyton, although I doubt if they are much read today. On their holidays the intrepid and ageless quintet invariably encountered a criminal gang engaged in nefarious nocturnal pursuits and defeated them with skill and derring-do. What Julian, Dick, Ann, George and Timmy the dog would have made of our Croatian Quiz is anybody's guess, but thanks to the Famous Five readers who tackled them on behalf of everybody else.
Before we take another look and reveal the answers can I say that these are really tough problems that might well have beaten anybody, because they are not easily solveable without a lot of thought. Each is in one way or another unusual and not responsive to the "usually I do this" method" that gets us through most situations.
Here's Position One again.

White is "stripped and stacked", a hugely inflexible position to be in. If she can't throw a life-saving double there is going to be a blot somewhere that Black, trailing by 8 pips after the roll, will want to hit. To take advantage of that he needs to cover his blot and over the board I would have tried 13/9, 6/4. This got one vote from the panel and is the third best play. It does beat 22/16 which got two votes, but that play fails on two counts. It doesn't make the four point board and it runs into a race where Black trails. It is a blot that has no useful function when it isn't hit; a blot on the landscape one might say. Another panellist tried 23/21, 13/9, but again, it doesn't make a four point board. It threatens to make it, but that is never as good as actually making it! Lastly we had one vote for 23/21, 8/4, which was also my student's play.
And the right answer is...............22/20, 8/4!
There is an excellent YouTube video where Falafel, Bob Wachtel and Michy discuss a play from Bob's match. Then Bob reveals the right answer as per computer rollout. Falafel says, "Now I know the answer I understand the position", which is very funny and also very wise. So, what is happening here? White's position is the key, because she is really stuck for play with her outfield points all stripped and her 6pt stacked. What XG's play does, after it has crucially made the 4pt board, is to deny White safe landing points. Playing 23/21, 8/4, the second best play although still a large error, allows White to dump checkers onto her 1 and 2pts and even more importantly, denies her the option of playing to the 11pt in relative safety with most twos and fours.

Position Two was a lot easier with only three posible plays.

Bar/20/14 got no votes from the panel, another "blot on the landscape", trying to race into a race where Black trails, although not by much. Bar/20, 24/18 got two votes and is the usual answer to this sort of thing, forcing contact while Black has the better board, in the hope of exchanging hits or making a high anchor. Three of our panellists went for bar/20, 13/7 and that is clearly best. It beautifully illustrates two themes that recur constantly. The first is that Black has killed two checkers on the ace point and fatally wounded two more on the 3pt, which is the casualty list when a 5-5 blitz fails. This means that his remaining 11 checkers all have to work extra hard, doing the work that is usually done by 15 men. In bg terms, this means more risk. In addition, Black still has a stack on his midpoint, 5 out of his 11 playable men in one place. I always put a mental flag on a stack that says "Urgent: please unstack me". It's no use saying, "I can't do that now, I've got other problems". Positional flaws like this have to be dealt with immediately. Again, in the immortal words of Falafel (possibly quoting Italo Calvi), "If not now, when?" The handy duplication of threes makes the medicine go down a little more easily.

I bet you can't wait for the other answers, but you will have to wait until tomorrow, as I have a flat to tidy before mrs dorbel comes back from her holidays.

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.
Mochizuki Masayuki v. Carlo Melzi, a 13pt IIBGF Match.

PayPal please and enquiries to dorbel(at)gmail(dot)com.

Until tomorrow, enjoy the game!

The Famous Five

2011-10-13T04:20:00.000-07:00

A little Quiz for you today, five puzzling positions from a student in Croatia. All of these are from money play, where as always the Jacoby Rule is in force and there are no scores to alter the value of gammons and the cube, so they should be easy, right? Let's see, in each position Black is on roll.

Position 1

Black to play 4-2. What and why?

Position 2

Black's 5-5 attack in the opening has failed miserably and now he has to play 6-5 from the bar. A choice of three sixes, so which and why?

Position 3

Black has already doubled and now has a nice 2-1 to play. This one will surprise a lot of you I know. What and why?

Position 4

Black to play a 3-1, neither easy nor obvious. What and why please.

Position 5

It has been said that the ability to play a poor roll well is "the calling card of a pro". This is a poor roll, so can you find Black's best play here? What and why please!

If you get all these right for the right reasons, then you should be writing your own blog. I'll be back in a day or two, with some of the thinking which might lead you to the right play if you meet these toughies one dark night.
Until then, enjoy the game!

Another Dorbelblunder.

2011-10-12T02:01:00.002-07:00

We left Black in this position last week, trailing 0-4 to 7 with the cube on White's side and apparently up the creek without a paddle. What is the correct cube action?
This is a handy reference position, easy to remember as White wins 88% of the games and 8 of those are gammons. At this score Black needs about 10% to take and redouble for the match, because that will be his equity if he passes and trails 7-away, Crawford. We can do lots of calculations to see whether White should redouble, but let me simplify it for you. At this score, it's almost impossible for White to have a correct redouble while there is a chance of a gammon.
Even leaving gammons out entirely, White's doubling window is so small, between 87 and 90% roughly, that her chances of ever being in it are minute. She'll either be not good enough, or she'll have a cash. Doubling now kills White's gammons and puts the match on the line, so playing on until those gammon chances have gone and then cashing is always the plan. In real terms, if White redoubles for the match, she'll be 88%. If she plays on and never redoubles she'll be 87.8%, but clearly she can do a lot better than that by using the cube to cash in all the games where her gammon chances disappear and retaining her 65% match equity in the horror games where she loses.
Player skills come into this. If Black is a world class player playing an intermediate, he should probably pass this, as his theoretical ME of 10% going into the Crawford game will be a lot better than that, because he will outplay White, which he can't really do if he takes this. From this it follows that intermediate White should turn the cube.
However, doubling does have one big plus for White. Humans hate to take and put the match on the line, so if White redoubles here, she will get a lot of wrong passes, from those who underestimate Black's winning chances and from those who know that the take is theoretically correct, but would rather try to win from 7-away, Crawford. In this match White (eberlein a very strong player) doubled and Black (me) feebly passed!
Doh! Tomorrow, if it ever comes, I have some lovely quiz positions for you, all of which were sent to me from Croatia. I forecast that this country has a very bright BG future, with a lot of good players improving fast and the Croatian Backgammon Federation - Hrvatski backgammon-tavla savez, up and running to promote the game there.
Until then, wherever you are, enjoy the game!

Blundalongadorbel Part 26

2011-10-08T04:25:00.000-07:00

It always pays to look at your own blunders. Sometimes when I'm short of other stuff to post I even show them to you, but only when they aren't too embarassing.
I played a 7 pointer with eberlein on fibs today, a very strong player. I kept it down to two blunders which I was pretty happy with, but first let's look at some cube action (and inaction) from game two.

I'm playing the Black checkers here, I'm on the bar and trailing 7-away, 3-away. Would you double this? It's a correct double actually, although it's only a very small error to miss it. Even though White has a better board (6-5-4 is much stronger than 6-5-3) and I am on the bar, it's a double, which just shows you how little you need to double something that has gammon threats when you trail!
I rolled 1-1 and played bar/24*, 11/10, 5/4*(2), although bar/24*, 8/7, 5/4*(2) might be a little bit stronger, because it doesn't give a 5-5 joker and the checker on the 7pt aims at the 1pt, which I might want to hit or make next turn. White rolled 2-1 to leave this next position.

I think we all know to double this one, as three men back against one is often a double anyway, so I doubled and White correctly took. She still has the best board, she's anchored, straightforward take. Then I threw 3-1 and how would you play that?
In the end I settled for making the 5pt and anything else is a blunder. Basically, it's going to be a long difficult game, cubeless for a long while yet, so I need the board in order to compete! 13/10, 11/10 wouldn't frighten a child.

Later still we got down to this. White leads 4-0 to 7 remember and here she doubled.

It's important to know your Match Equity Table here. Is White's double correct? Should Black take if she does double? Let's leave the answers to these and other burning questions until tomorrow!
Until then, enjoy the game!

Must You Go?

2011-10-06T06:05:00.000-07:00

I said in the last post that I would show you some more slotting the bar positions, but the sequence that I had in mind turned out to be less interesting than I thought and covered much of the same ground, so here's an interesting little late game sequence that caught out a strong player with the Black checkers. See if you can do better, not sure I would have done!

This position that comes up a lot, so worth knowing what to do with cube and checkers. It's 3-away, 3-away, cube centred, Black on roll to play 2-1, but first, should he have cubed before this roll?

I don't think many people would cube this. White leads 67-84 in the race and although that count is distorted by all those checkers on the low points, it is a lead. Nevertheless, Black is a 2/1 favourite in this position and on roll, wins 66% of the games! At this score, that's very close to a cube and turning it now would only be a small mistake. Note that the score makes a difference, as you can cube a bit earlier tied 3-away. There is one caveat though. If you want to double, you have to know how to play it, or you can give away a lot of equity here. White's play will be trivially easy, often forced, whereas Black can mess this up. Really? Isn't this simple for Black?
Let me show you, but before we go on, write down the three best plays of 2-1 for Black and put them in order.
Done that? Most people here play 10/7. Aware that it's a problem, some people will say, "That's too obvious" and play 8/7, 8/6, creating two spares. I bet not many will spot the imaginative trap play 7/4, but it's clearly right and right by a lot. Playing 10/7 gives away almost 1/10th of a point! 8/7, 8/6 is even worse.
So, why leave a shot? It's because Black's winning and gammon chances go up when he can force White to leave the anchor. If White has to hit on the way, then Black can just recirculate with good chances of picking up both checkers. If White can't or won't hit, Black has lost nothing and has slotted a valuable point.
Well, in the match Black played the stolid 7/4 and White played the forced 4-3, 20/13, which leaves this next position with Black on roll. Should he cube?

If he was close to a cube last time, Black must have a cube now, even though he has fallen behind in the race. This is because he now has attacking chances to hit and/or point on White's straggler. These lead to market loss if White can't respond, which means volatility which cries out for a cube turn. Sadly, Black didn't cube and rolled 6-4.

10/6, 10/4 right? Well that's what he played, but it's a blunder. The play is 8/4, 7/1! Why? partly to keep fives blocked, but mostly to force White to hit with her threes, recirculating a Black checker to try and pick up White's runners as they come around. After the match play, White stepped out and won with the cube.

Just because it looks simple doesn't mean that it is simple. Remember too that you have to look at all the checkers on the board. If the race was closer and White had a better board, as she would, then the right plays change a lot. A three point board or less is essential for trap plays. However, if you find yourself in Black's position, as you will from time to time, don't miss your market with the cube. The defender is very vulnerable when she has to leave that anchor.

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.
Mochizuki Masayuki v. Carlo Melzi, a 13pt IIBGF Match.

PayPal please and enquiries to dorbel(at)gmail(dot)com.

It All Depends

2011-10-03T07:20:00.000-07:00

Some questions seem to pop up time and again, but we never quite know the answer. Here's one a student asked.
"I have a five point board from the 6pt to the 2pt, my opponent is on the bar. Should I slot the bar to try and make it, thus giving him the joker 6-1?" As you may have guessed, the answer is, "It all depends." Depends on what?
Take a look at this series of positions. It's post Crawford, White has the cube and is on the bar. Black rolls a 6-3.

Slot the bar? You have three questions that need to be answered. How close is the race? How close are you to winning the game? How useful is this number if you don't slot?
So, race. Black still trails 124-115. This argues for slotting the bar. You need to contain White if she enters, to stop her from jumping out into the race and/or hitting a fly shot in the outfield.
How close are you to winning the game? Not very, there's still a lot to be done bringing those back checkers round and making the bar will be a big help. This argues for slotting now.
How useful is the number if you don't slot? Not bad, it escapes a back man, but they shouldn't have too much trouble getting away later, so I suppose the answer here is neutral.
So, two votes for a slot and one don't know. Slotting is correct and 24/21, 22/16 or 24/21, 16/10 (preparing to make the bar naturally) are small errors.

Moving on a roll Black didn't slot, White danced and Black throws 6-3 again.

Now the race is tied before the roll, 115-115, so it's less important than before to contain White if she enters, but still worth doing. If White enters next turn, she'll have good racing chances. Black still has a bit of running round to do as well and locking up the six prime will make it much less stressful. As to being useful elsewhere, Black can play 21/15, 16/13. This continues the escape and usefully now gives 6-6 to complete the close-out, as well as 3-3 and 6-2 to make the bar naturally. However, on balance it looks like we should still slot and that is the right play. 16/7 is worth the risk, although it's closer than before and the alternate plays are now only mistakes costing just under 0.03ppg.

Note with the above two positions, we are offering a lot of fly shots by slotting. It's not only 6-1. If it's correct to slot with this amount of risk, obviously with less risk it would be even more atrractive, in fact it's harder to imagine more risk than having five blots spread out around the board, although paradoxically it is these blots that are the reason why we need the bar so much! We'll breathe much more easily with a six prime.

Black doesn't slot the bar and after another White dance Black rolls 5-3.

Black has improved, White has done nothing. Black can still slot with 15/7, but several things have changed. He's gained a lot in the race, making it less necessary than before to complete the prime. He's much closer to winning, as he has escaped everything and reduced the fly shots. He can also play this quite usefully in other ways, either by cutting the fly shots down to zero (16/13, 15/10) or perhaps better 16/11, 9/6, preparing to hit on the ace if White enters. The numbers to make the bar naturally have also gone up. After 16/11, 9/6, Black has 6-6 and 5-5 to complete the closeout, as well as 4-4, 3-3 and 6-4 to make the bar naturally.
Where does that leave us? Now slotting the bar is probably minutely wrong, certainly not a bad play but according to the rollout, wrong by 1/100th of a point!

What we have seen here is a nice natural progression from clearly right to slot the bar up to maybe/maybe not. If White dances again, we should see a position where slotting the bar is clearly wrong. Black played 16/13, 15/10, the joker control play and White danced again, whereupon Black rolled 2-1.

Again Black has improved, both in the race and positionally. He can come home from here without making the bar at all and in any case he has 3-3, 2-2, 6-3 and 6-2 to make the bar naturally, as well as 6-6 to complete the closeout. Giving even 6-1 from the bar is no longer worth the candle and the best play is 13/11, 9/8.

Tomorrow I'll continue with this theme, when we look at whether it is right to slot the bar when the opponent is anchored on the ace and has a man on the bar as well.
Until then, enjoy the game!

On Sale Now

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.

Better known as Mochy and Falafel, these two giants played brilliantly in this 10 game match. It is now available as an XG file, analysed and annotated by me and with the annotation approved and extended by both players.
It costs just $10 and is sure to be of interest to keen students at all levels. For those of you without XG, it is available as a .mat file for Gnu or Snowie at the same price, with the same commentary in a separate document. Orders to dorbel (at) gmail (dot) com, payment by PayPal please.
If preferred, you can pay 8 euros, or for UK readers 7 pounds.

Aslo, just completed, Mochizuki Masayuki v Carlo Melzi, a 13pt IIBGF match. Annotated, with rollouts, all as above, same price. Shop early for Christmas.

On Sale Now

2011-09-28T08:49:00.000-07:00

Mochizuki Masayuki v. Matvey Natanzon, a 13pt IIBGF Match.

Just Whack It.

2011-09-28T01:40:00.000-07:00

We all go there, the game's nearly won, we are rolling a prime home, but the opponent pops up a blot. What to do, hit it or ignore it? Inevitably the opponent has a strong home board. If she doesn't, it isn't a problem because we don't risk much with the hit. What's the rule? As ever, it depends. Look at Position One.
Black leads 2-away, 3-away, the cube is in the middle and White has a checker on the bar. Black is correctly playing on for a match winning gammon. What to do here, hit or make a quiet play?

One way to approach this problem is to estimate your gammon chances if you hit and your gammon chances if you play safe and adjust those for the gammon price at this score and ideally do the same for your opponent, bearing in mind that at this score her gammons will be almost as dangerous as yours, getting her to Crawford. You can also look at the weather forecast, your horoscope for the day and the stock exchange closing prices, but we are already doing too much work. Just whack it! Why? I use the Glad/Sad ratio. If we hit, White dances 70% of the time and we are very Glad. We are big favourites to closeout and win and with two checkers on the bar and three other crossovers that White needs on the far side, we win over 50% gammons. Closing out two checker is usually 40% or so and three crossovers is a roll and a half. When White hits (30%) we are a bit Sad, but we still have some chances to enter and jump and if we can do that we must pick up two more checkers! If we play quietly and White rolls a two, then we will probably turn the cube and cash, so no gammons there at all. A 70/30 Glad/Sad ratio is pretty hot at any time, hotter here when the 70 contains 50 gammons and the 30 just means we get doubled out.
Now you may criticise this technique as crude and point out that it ignores many other possibilities. You'd be right. I haven't counted the times after the hit when we fail to cover, or the times when we choose not to hit and still make the 2 point next turn anyway. I haven't allowed for the possibility that White may be able to double us in and win a doubled gammon. On the other hand the attempt to be more precise and estimate gammon rates also suffers from this problem.
There is another reason why we need to hit here. We do need to make the point for the bearoff and every roll that we wait to throw a natural point making number it gets harder. It's harder to make the deuce than it would be to make the ace, because there are fewer checkers to do it with. One enemy checker on the deuce, or even an empty point and men on the bar can be very inconvenient, a phenomenon known as a phantom deuce point game.
Convinced yet? OK, if you are White in that position, do you want to be hit or would you rather be left alone? If White would rather be left in peace, it must be right to hit it. Always do what the enemy doesn't want you to do. I must stress that in this position, the unusually high value of gammons to Black is key. If a gammon didn't count for much, no need to let White back into the game by giving her a shot. Let her have her deuce point game by all means. It doesn't ever win, because you will just double her out.

This next position illustrates some of these points. Black leads 2-1 to 5 and has the cube, White is on the bar.

In the first position, Black's Gammon Price is 1, twice as valuable as for money. Here on the other hand, it is .40, less than for money. The GP in a match is your ME for winning a gammon minus the ME for a plain win, divided by the ME for a plain win minus the ME for a plain loss.
Here that is 100-83/ 83-40 or .40. So, here, hitting here would be quite wrong, partly because we don't gain much from a gammon anyway, partly because it is easier to make the ace than the deuce and partly because we risk a horrendous gammon loss, with the whole match down the drain.
To use the Glad/Sad test it is split 70/30 like before, but now the Glads are fairly Glad, but the Sads are very Sad indeed, going behind in the match when we lose a plain game and losing the whole thing when we get gammoned.

By all means go for a pure analytical approach, where you need an accurate estimate and an accurate use of some mental arithmetic. If you can cope with that, then this is what most of the top pros do. For most of us though, me included, instinct and experience need to stand in for the hard slog of calculation. Just Whack It!

By the way, failing to hit in position 1 is a small error, hitting in position 2 is a blunder!

Until the next post, enjoy the game!

Make Mine A Double Answers.

2011-09-19T04:14:00.000-07:00

Thank you yuri, dnikeeb, timothy, ah clem and markx for your illuminating reasoning, heroes all.
Let's look at these again, with hindsight and the benefit of a computer! This first one was a misplay of mine.

"Should I hit him on the bar? That's a waste of a good number, I'll just play the solid 13/11(2), 6/4(2). I didn't even consider 6/4(2), 3/1*(2) but it is easily the best play, very like the position after an opening split (for White) and a 5-5. When White dances you can cash the game. You won't be too good. When he enters, well at least you have a three point board and often two or three blots to shoot at. If White enters with a 6, you can probably double and get a take, although weaker positions than this are passed every day. Any other play is a BIG blunder.

This play came from 23 years ago. White is Alan Steffen, Black is Joe Sylvester and Joe took half an hour to make his play. Joe played 10/1, 4/1. He eventually did this as the best anti-gammon play. Danny Kleinman commented that he would play to win 11/8*, 11/5, 10/7. There were almost as many other ideas as there were experts! In 1988 of course, there wasn't anybody with a laptop and a bot.
Both the best play include 21/18(2). This seems so obvious to me, because it gives White no "safe" points. If you stay back she can leave blots on the 13, 12 or 11 pts and only risk an indirect shot. After that you pick up the blot on the 10pt and play 7/4 or 4/1. The two plays are roughly equal. How did Joe's "gammonsaver" play do? It's probably fourth best, winning about 29% and losing 10 gammons. Danny's "play to win" approach wins 33% but loses 20 gammons! The winningest play is 21/18, 11/8*(2), 10/7, earning 36 wins but losing 28 gammons!

Finally this one.

It's double match point. 13/9(2) is the clear winner, putting you just one roll away from making a 6 prime. Even when White rolls a 2, you are far from dead of course. making the point 6 pips away from a straggler is always strong, so that he can't jump out with a single die. To many people's surprise I am sure, this is also the right play for money. You cash when he doesn't roll a 2 and you are still in the game when he does.

How did our brave correspondents fare? One fell nobly on his sword after feeding the positions into Gnu, another had three wrong answers, another one right, another two right and dnikeeb nailed all three. Kudos to dnikeeb of course, but equally kudos to the others for sharing their thought processes here, from which we and they can learn a lot. We only learn from mistakes. Our successes teach us nothing.

I'll find something else for you tomorrow. Don't forget to order your copy of Mochy v. Falafel, annotated and with comments from the players, the most instructive match I have seen for ages with many tough plays. dorbel(at)gmail(dot)com for PayPal and/or queries. $10.
Until next time, enjoy the game!

Make Mine A Double

2011-09-17T08:19:00.001-07:00

It's noticeable that a disproportionate number of errors occur with doublets. I suppose this is to do with the fact that you have to move four checkers instead of two. The smaller the doublet, the greater number of choices usually and the greater the chance of a mistake. Here are three postions for your careful thought. As always, comments and reasoning greatly appreciated.

Position 1

No score in a 9 point match. Black to play 2-2.

Position 2

Black leads 3-0 to 21 and has 3-3 to play. No clocks and Black took half an hour to make a play here! His opponent read Bertrand Russell! Some kudos for anybody who can name the players.

Position 3

Double Match Point. Black to play 2-2. Would it make a difference if it was a money game?

Have fun and while the comments flood in from the usual suspects, enjoy the game!

Free Sample Answers.

2011-09-13T02:39:00.001-07:00

A big thank you to Timothy, Clem and Julia for their thoughtful contributions.

This is the first one and all the team chose to make the Golden Anchor.

Falafel actually chose the hit, which is a small error, after considerable thought. Would our panel have done the same over the board, i.e. not presented as a problem? Nobody will ever know, so kudos to the panel there.

Timothy and Julia both liked 9/3*, but I am afraid that that is way off beam. With four men back, White's blitzing options are very poor, due to shortage of ammunition. Falafel correctly covered the 9pt and played 23/21. This is second best, a medium error and the best play is 20/18, 13/9. With this, White blocks sixes from the back and the midpoint, forcing Black to play them deep into his home board, generating lots of shots for White. This is an unusual situation, as it's rarely correct to switch from the 20pt to the 18pt this early in the game. Hard to find over the board or as a problem. I can't really say I would have hit on it.

Lastly, the play from game 9. Mochy lead 1-away, 3-away, Crawford. Black trails in the pipcount 146-152 before the roll.

A unanimous verdict from our panel, as indeed there was from the peanut gallery on GridGammon. Hit twice is correct and Mochy's play of 13/8, 9/8 got the bird. It isn't terrible, a small error at worst, but 8/7*. 6/1* is best, better than hitting once because fewer shots.
Although it's the Crawford game, Mochy should make an anti-positional play and hit. He needs to put White off-balance for a roll, otherwise White will just move ahead in the race and improve his poition at leisure.

To illustrate the dangers of generalising from this though, look at two more positions. The first comes from the first game of this fascinating match. Mochy is on roll with what looks very like the one above. It's game one, so no score to 13.

Now the answer is 14/8 by a very small margin over hitting twice. Here Black leads in the race 157-169 and has three men back against one, encouraging him to play safe. The big surprise though, is that if you choose to double hit, 8/7*/2* is correct! When you play 8/7*, 6/1*, you duplicate your own sixes and also leave four blots instead of three. This counts for a lot when it comes to tidying up.

You all see this position often.

Everybody knows that you hit twice with 6-5, but what about 5-1? Then it's incorrect and just 13/7* will do nicely. At GammonGo the double hit is almost equal. Note again the duplication of your own sixes after the double hit.

I hope you learned as much as me from these positions. You can see all of the Mochy v. Falafel match on an XG file, with rollouts and annotated by me, with comments from Mochy and Falafel. It costs $10 US, 7-50 euros or 6-50 pounds sterling. It is also available as a file that can be read with Gnu or Snowie and as a Word doc. for the more "hands on" types who like to learn on a real board. For the Word doc., add 50%, which will also include the XG or Gnu file.
Paypal to dorbel(at)gmail(dot)com please.
Until the next time, enjoy the game!

Free Samples.

2011-09-10T09:35:00.000-07:00

I'll start with an apology for not posting for a week, as I've put all my backgammon time into analysing and annotating a 13pt match between Masayuki and Natanzon, better known to us all as Mochy and Falafel. Played on GridGammon they entertained a large crowd with 10 games of world champion level play and their amusing comments. This match will be available in a day or two, as I am just waiting for comments back from the players on some key moments, then you can purchase it for $10 in one of two formats, for eXtremeGammon or as a .mat file for the other bots. Both versions will contain all the comments, based on XG rollouts, which will make for an interesting comparison with the older bots! For those of you without one, the match will also be available as a Word doc. containing all the rolls, plays and commentary and about 50 board diagrams, so that you can follow the match with a backgammon "board" as they are known. The word version will be $15, as a lot more work is involved.
Other currencies for the match file, 7-50 euros, 6-50 pounds, 9-50 dollars Aus. or 800 yen. Add 50% for the word doc. version.

To whet your appetites, here's just three positions. How would you have handled these?

The first comes in Game Three, with the match tied at 4-4 and White (Falafel) is to play from the bar.

The second comes in Game Six. Mochy now leads 8-6 and it's Falafel to play.

And last but not least, a tough play for Mochy from Game Nine. It's The Crawford Game, 12-10 to Mochy.

What will you do, what did the experts do and were they right? I'll let you know the answers in a day or two. Advance orders for this excellent match, with annotation by me and comments from the players, by PayPal to dorbel(at)gmail(dot)com.

Until the next post, Enjoy the game!

Mochy v. Falafel

2011-09-01T01:48:00.000-07:00

If asked to select the two best players in the world today, the names of Matvey "Falafel" Natanzon and Mochisuki "Mochy" Masayuki would be in anybody's short list. Last night on GridGammon in an IIBGF match, they played a 13 pointer that kept the gallery enthralled for two hours, with a dazzling exhibition of world champion level play. Neither made any blunders and both played with a PR of under 2 on eXtremeGammon. I'm spending the next week annotating this match and together with comments from Mochy and Falafel, it will be for sale at a price of $10 for an XG, Snowie or Gnu file, or $15 as a Word doc.
Studying annotated matches of high class players is one of the best ways to improve your game. Don't miss this one.

One From The Vaults.

2011-08-31T01:20:00.000-07:00

Back in the Old Days, before the bots took over the task of teaching the world to play good backgammon, there were expert players and analysts who presented their matches for us, so that we could learn. How good were these players? How good were the analysts? Just running their matches through a modern bot and looking at numbers, they weren't great. Considering that they learned to play without all the aids that we have, they were terrific!
In the next few posts I am going to look at a match played in Monte Carlo in 1981. The players were both at the top of the tree in those days, Stanley Tomchin and Chuck Papazian. We have the match because it was recorded and annotated by Kent Goulding in his series "Backgammon with the Champs." Let me say before we start though, that no comments that I make about the plays or Kent's commentary are in any way intended to poke fun. These were great players and the analysis is terrific. We stand today on the shoulders of giants.

Play in those days was different. The checker play was very pure, concentrating on keeping all your checkers in play much as we do now in dmp games. They slotted the 5pt a lot, noticeably with an opening 6-2 as well as aces and an opening 5-3 was played 13/8, 13/10 by most people. These plays are occasionally seen even today, although now known to be weak. Oddly neither of the players in this match minded hitting on the ace point, but usually only as a diversion. They didn't like to actually make it. In general though, their checker play was excellent, but in comparison to modern players their cube action was poor, with both players passing a lot of easy takes. This 19 point match lasted for 27 games because so many games finished at the 1 level.

It's Game One. Papazian (White) has a 4-1 to play. How would you handle it?

Position ID: mGfwATCYZ/ABMA
Match ID: MAFmAgAAAAAA

I expect (and hope) that you picked 13/9, 24/23, unstack and split. White went for 13/9, 6/5 because that was the way that they played then, with a big emphasis on making the 5pt and building a prime. Can we say why that is wrong? It comits to one plan, building a prime, at considerable risk of being hit. The modern play is much more flexible, allowing White to develop one of several different game plans depending on what the dice provide next, without the same degree of risk. You could of course play 13/8 entirely risk free as far as being hit is concerned, but no more flexible next turn than it is now. That would be an error.
Many players in assessing the risk of a slot count only how many shots it takes to hit that blot. It's as important, perhaps even more important to count how much you lose when hit. If you slot the 5pt here and get hit, you lose 20 pips immediately and given that 11% of the time you then fan with four of your biggest numbers, 6-6, 4-4 and 6-4, a hit loses you three full rolls on average! That's a lot in a game that is at heart a race. How bad is the play? It costs you just about 1/10th of a point compared to the split play. That's a big error. KG thought that the split was a reasonable alternative, so we can deduce that slotting was widely regarded as the standard then for this sort of situation.

Well Black did hit and White did fan, producing this position with Black on roll. Before reading on, what's the correct cube action for both sides?

Position ID: WGfwAFiYZ/ARIA
Match ID: cAlgAgAAAAAA

Black (Tomchin) decided not to double. This is correct, although he is nearly in the window. KG nailed this one, saying that giving away the cube was too big a price to pay for the small number of market losers. Would you double this? In the first game of a long match there's a lot to be said for a very aggressive double like this. Black will win about 62% from here including 24 gammons, to go 2-0 or 4-0 up. If things go White's way, Black will find out how well White uses a 4 cube, extremely valuable information at the start of a long match. Last but not least, you may get a pass! I've seen weaker doubles than this dropped. There are some later on in this match.

Later, White has to play 1-1 from the bar. What would you do?

Position ID: mLfgESBYZ/AAWA
Match ID: MIFkAgAAAAAA

As a fanatical primer, Papazian entered and made the bar and the 5pt. The modern players, knowing that three checkers on the 24pt is deathly will probably make the 23 and 5pts and they'd be right. Improving the 8pt to the 7pt isn't hugely stronger anyway.

A little while later the game moved on to the sort of priming battle that so often occurred then, because of the way that they played. Black is on roll. Is this the sort of thing that you double? As White, would you take?

Position ID: 2G7BADTYbsEDIA
Match ID: cAlgAgAAAAAA

Black doubled, White took, correct action on both sides. The primes are identical, but Black has two extra outfield checkers to play with, which will mean that he will win the priming battle all other things being equal, because White will usually bust his prime first. White still has a lot of play himself though and note that cube ownership is very valuable indeed in prime/prime games, with the ever present possibility of the doubler going bust at any moment with a large awkward doublet. Also, White is at least anchored and can usually fall back on an ace point game if nothing else. KG thought that the take/pass decision was close and came down on the side of pass. That is a blunder, but an understandable one I think.

In this next position, Papazian (White) has to play 6-4.

Position ID: 2G6DAyDYbsEANA
Match ID: AQFzAgAAAAAA

So fanatical were they in sticking to their plan, White plays 13/7, 13/9 here. Today, everybody would make the 2pt without even thinking about it. No shots, makes a point, preserves the midpoint, what's not to like? This play and the play of 1-1 earlier drew no comment from KG, indicating clearly that this was the accepted way to play, pure, brave and stick to your plan.
Modern players need to be more adaptable, switching from one plan to another as needed, often several times in a game!

I'd hate to show you just mistakes. See if you can find Tomchin's lovely play in this position, Black to play 5-2.

Position ID: atsEADbY7TYBAA
Match ID: QYlqAgAAAAAA

He played the elegant 11/6, 5/3, well ahead of any other play. White won't hit even if he does throw a 1, so the perfect slot, risk free, efficient and safe next turn.

We'll look some more at this fascinating match tomorrow. Until then, enjoy the game!

Note: I've switched back to using Gnu boards and ID's, as Gnu users by far outnumber ExtremeGammon users at present. However, I am using EG for the analysis. I'll let you know if it is ever widely different to Gnu.

Fibs Holiday Answers.

2011-08-27T03:35:00.001-07:00

Well big thanks to both the readers who posted comments for us and smaller thanks to those who gave me their answers on Fibs and no thanks at all to those who couldn't be bothered! This is not a Dark Ride, you need to participate!

Position One

XGID=-a--aBC-Ca--eC--Ab-cb-A-B-:0:0:1:32:0:4:1:5:10

Black leads 4-0 to 5, Crawford.

Just sitting on this position with an ultra quiet play, 24/22, 16/13 is not really an option. Black does need to hit White off the 4pt, as you usually do when your opponent has a blot at the edge of your prime. You want to make it and you don't want her to make it. Black can't be doubled and loses hardly anything by being gammoned, so he should be playing with a lot of freedom anyway. There are three plays that are slightly better than the quiet play, 8/5, 6/4*, 16/13, 6/4* and 6/4*/1*, all very small errors costing about 0.03ppg. I wouldn't argue with any of these plays if a doubles partner wanted to make them, but the standout best play is 24/21, 6/4*.
Phew, five blots, can it be right? It can here because White is unusually short of checkers to attack, with only seven checkers in the zone and an awkward stack on the midpoint. This maximises Black's opportunities at the back, with enhanced chances to anchor, escape or hit in the outfield as the dice dictate, at a time when White can't mount the sort of response that usually inhibits such a wide open play.

Position Two

XGID=-a-a-BB-Ca--cC--Bbbcb-A-B-:0:0:1:42:0:4:1:5:10

The same game later. Actually this isn't too hard. 24/22, 13/9* is best, hitting and improving the anchor. My student played 13/9*, 8/6 but our correspondents didn't fall for that. If you did, 8/6 looks more flexible for the attack, but with only eight checkers in the zone that attack isn't coming soon and Black doesn't really want to break the 8pt to hit. Also, that spare may be useful to make the bar, so it has a dual purpose where it is. Three checkers back always argues powerfully for a high anchor anyway.

Position Three

XGID=-a-a-BB-Ca--cC--Bbbcb-A-B-:0:0:1:42:0:4:1:5:10

Same game.

This is a tough play to find. I instinctively liked 16/10, 13/10. It's usually good to make the point six pips away from the opponent's anchor. That play is just about equal with 22/16, 6/3* and both are well ahead of anything else! Phew again, what is going on here? Leaving your anchor and hitting loose behind White's anchor, with the race evenly poised and White having a stronger board! Sometimes answers defy my ability to analyse even with hindsight, so if anybody has any clues about this one I'd be pleased to hear them.
Here's what I think. White's shortage of any spares anywhere near her home board and the blot on her 2pt are of course factors which make the loose hit less dangerous than it otherwise might be, but you do have to ask, what does Black gain from this risk? It's this. Neither side at present has any points made in the outfields, apart from the midpoints and this is a big positional weakness for both sides. Either of the best plays remedies this for Black and with the game so evenly poised, it's hard to say whether the defensive 16pt or the attacking 10pt are going to be more useful.
Even when games reach this sort of tense stand-off, with a hard play every turn, we must keep trying to address severe positional weaknesses, even at the cost of some risk. If we don't do that when we can, then the game will only get harder as it goes on.
I learned a lot from these positions and if you did too, then it's well worth the effort. Keep writing in those that do and start writing in those that don't! It's a better blog with your contribution!

On August 31st at 2300UTC on GridGammon, two of the elite will go head to head for a 13pt IIBGF match. They are Matvey "Falafel" Natanzon of Israel and Mochizuki "Mochy" Masayuki of Japan. This match will be recorded, annotated by me and comments from both these players will be added. It will be available with the annotation and comments as an XG file for $10 or as a Word doc. for $15. Versions as Gnu or Snowie files can also be made if there is a demand at $10.
This is your chance to see how the very best players in the world think and play. It should be a terrific learning aid.

Enjoy the game!

The Fibs Holiday Quiz

2011-08-25T01:28:00.000-07:00

Sorry to have been away so long. I occasionally have to interrupt backgammon for life!

Here are three nice checker play problems for you, taken from a recent lesson. As an experiment, I am using my new toy eXtremeGammon to make the diagrams. Hope you like them, but if you don't I can easily revert to the old wooden boards.

Position One

White lead 4-0 to 5 and it's the Crawford game. Black is on roll. Several plays suggest themselves, what do you like?

Position Two

Same game a bit later on, Black has a 4-2 to play.

Position Three

.......and still in the Crawford game, Black to play 6-3.

Answers please, but as ever, your reasoning is much more valuable than the right play!
Enjoy the game!

Japanese Cube Answers

2011-08-18T05:01:00.000-07:00

Well, thanks to the indefatigable ah-clem for giving us his thoughts. Let's see how his judgements compare with those of these top-class Japanese players and with the bot analysis.

Position 1

0-0 to 23, Black (Mochy) on roll and he doubled this and White (Suzuki) took. This is actually a bit early, a small error by Mochy. Black has three men back against White's one, which is a weakness and also trails in the race by 10 pips before the roll. Why then is such a great player doubling? Well he has the 6-5-4pts made while White has made nothing yet and he is also looking at White's very awkward stacks on the 8 and 6pts. This could easily go very wrong for White very fast and the momentum to be gained by winning a doubled gammon in the first game is valuable. If things do go White's way, Black is also going to find out how well White uses the cube, very valuable knowledge. With Black's high anchor to insure against an immediate bad sequence, I still like this double even though technically it is a bit light.

Position 2

Of all mid-game positions, I find prime v. prime to be the hardest to evaluate, or even analyse coherently. Let's try! I think White's double is absolutely clear. He has one man back against three, he is shooting at a blot, he already has a five prime and if he doesn't hit, he has three checkers in the outfield that he can fiddle around with while he waits for Black's front position to crumble. In technical terms, White is said to have better timing. What does Black have going for him to justify a take? Well he is anchored at the edge of White's prime, he has a great board and he still has a potential six prime of is own. You also need to add to this the fact that cube ownership is more valuable in prime/prime battles than in any other form of the game. This is because one bad roll can see you go from underdog to favourite in a moment. Double/take is correct and that is what happened in the match.

Position 3

Black didn't double this, not sure why! 23 numbers put White in the air against a four point board. Anything that doesn't hit is an above average racing roll of 9 pips or better and gives Black a nice race lead with a high anchor. White's distribution is also very poor, but it's still an easy take. He's in good shape after the non hit numbers and will be a favourite to enter even if hit. Look out for positions that have this level of volatility, they cry out for a double. Double and Take.

Position 4.

White must double this but Black can still take. He is anchored and anything may yet happen. Both sides have three blots, so it is extremely volatile, like the previous position. Double and Take.

Position 5

White has a huge race lead here but Black should redouble and this is already a clear pass! Why is Black's position so strong? If we look at what White needs to do to win it will give us a clue. He needs to enter, escape and make his way through an outfield which Black is about to flood with hitters. His task may get even harder if he enters with 1-4, 2-4, 2-3 or 2-4 and has to expose another blot and harder still if Black can make his bar point or 8pt. In effect, Black's position will get stronger roll by roll while White's gets weaker. Black didn't redouble, White danced, Black then did redouble and got a take in a position that is an even bigger pass of course, so Mochy's conservatism paid off big time. Redouble and pass is correct.
So there you have it, ah_clem made some mistakes but the 2010 world champion made some mistakes and so did the 2011 champion, so perhaps we shouldn't be too tough on him! I hope you found these interesting, as I did.
Hard game backgammon! Until the next post, enjoy playing it!

Japanese Cubes

2011-08-12T04:23:00.000-07:00

I have been lucky enough to get the file of the World Championship semi-final between Takumitsu Suzuki, the eventual champion and Mochizuki Masayouki, the defending champion from 2010. Astonishingly they went to the same High School where they knew each other through chess, although Mochy is the older by two years.

Let's take a look at some of the cube decisions. Here are five of them for you to think about for a day or two.

This is the first game of a 23 point match and Black (Mochy) is on roll.

Position ID: 4PMxAwjYnsEAIw

Match ID: cAngAAAAAAAA

Cube action for both sides?

Position 2 is a bit harder, White (Susuki) is on roll. Black leads 2-0/23

Position ID: bFsjABa4bRMDIA

Match ID: MAHgAAAAAAAA

Cube action?

Position 3, another "easy" one, or is it? It's 2-2/23 now and Black is on roll.

Position ID: mLkwwCnM5sgBCQ
Match ID: MAHgAAAAAAAA

Cube action?

Position 4. Black leads 3-2/23 now and it is White on roll.

Position ID: mLkwwCnM5sgBCQ

Match ID: MAHgAAAAAAAA

Cube action?

Lastly for today, Position 5. It's the same game and Black is on roll and White is on the bar. Black owns the cube.

Position ID: 7z0DAEBsN8gABw
Match ID: UQngAAAAAAAA

Cube action?

If you can get all of these right for both sides, you can be very proud of yourself. Give it a go and let us know your reasoning too. I ask for this for two reasons. First, you may well think of something I haven't thought of which is good of course. Second though, being able to assemble your thoughts and say why you want to do what you want to do is a key skill that will help you play better in real life. Watch a top doubles team in action. Listen to their reasoning. Imitate it.

I'll give you the answers to these in a day or two, until then, as ever, enjoy the game!

Quiz Time Answers

2011-08-10T03:18:00.000-07:00

All right, I know it isn't Friday, but you've had long enough. Thanks to those who used the comment feature for their thoughts and also those who gave me their answers on Fibs.

Position One.

Here's a very useful tip. "It's usually worth leaving an outfield blot if you can use the roll to make a good point inboard". 13/5(2) puts some teeth into Black's board and will make White very wary of plays that leave blots. If you don't make this play and instead pick up your blot with something like 13/9(2), 8/4, 6/2, White will cheerfully attack your straggler with anything she can find to throw at it. In addition, you have burned your spare on the 6pt and stacked a fifth checker on the 4pt, so you have more or less trashed your chances of ever making a strong board in future. Politicians learn, "It's the economy stupid". We might say, "It's the board stupid". Make it and don't break it.

Position 2.

This one took me by surprise. If it isn't a quiz it takes a very strong minded player to look for something else after 24/13 and a very skilful player to identify the right play.
Here are the steps. Black still trails by 15 pips after the roll, so a racing play is NOT indicated. 13/11 adds a sixth checker to a point that is already fat. I know we do that on the opening roll, but then we lead by 11 checkers after the roll. Here we can find a much better play and it is 13/7, 13/8. This unstacks and puts two very useful checkers into the zone. White's 16 hitting numbers hurt much less than usual because of that big gap in the middle of her board.
Running does nothing to apply pressure on White. It doesn't try to rectify Black's severe positional defects, in fact it makes them worse. A third alternate is the old Kent Goulding play, 24/18, 13/8, which bids to make a high anchor or exchange hits, but this is weaker than running. When it works, Black still has to put his frontal position together, when it doesn't, you get cubed.
What can we learn from this? We still need to address severe positional defects (stripped 8pt, stacked midpoint), even when we are behind in the race and outboarded, in fact particularly then, otherwise the game just drifts away.

Position 3.

Dang, missed everything, can't make a point, what shall I do, run? 24/20, 13/8? Actually though, Black hasn't missed everything. Hitting loose on the ace point is not a play anybody likes to be seen making, but there are times when you have to turn Mother's picture to the wall and do the ugly thing. 24/20, 6/1* is the best play. This is entirely a diversionary play designed to take away half of White's next roll. You won't achieve much by it, because either she hits it (bad) or she misses it (also bad), but at least you've slowed her down a bit, given her a a few awkward rolls and defused some of her jokers.

Position 4.

Black here is me and yes I played 13/3 but the wide open 13/7, 6/2* is best, by a lot. It leaves 23 shots and three blots but Black is anchored at the edge of White's front-loaded prime, so a few more checkers back isn't too bad. Be bold, when it works it's terrific, when it doesn't you're not dead. I wimped it, don't do as I did, do as I tell you. Fortune favours the brave.

Position 5

White lead, 8-6 to 9.

This one shouldn't keep us long, hitting is hugely correct, stopping White from anchoring and going for the closeout. This isn't always correct; if White's board was stronger then making the bar and attacking later could well be better, but here with White's blot on the 5pt and two point board Black has to blitz. Again Black is me and another pretty poor play as I played bar/23, 13/7. If you find yourself prone to these, perhaps like me you are too influenced by recent events. If I've been hit a lot lately and seen a lot of big turnarounds I tend to make these non-comittal plays and hope that the match will somehow win itself, which actually here it did, but that isn't the point. Try to approach each position with a clean slate in a nice objective way. Good trick if you can do it!

I do hope you learned something here, I certainly did. I'll try to find you something interesting for tomorrow. I have eXtreme gammon now, which is nice, but I'll keep on using this wooden Gnu board for the diagrams if that's ok with all of you. I can't say I like the XG graphics so much.

Enjoy the game!

Quiz Time

2011-08-08T02:06:00.001-07:00

Let's have a little quiz to start the week. All of these have some interest, none are easy. Don't assume that because it is a quiz that the obvious answer must be wrong! Just make the move that you would make over the board, with a little extra thought perhaps and let me know what you think. I'll post the answers on Friday.

Position 1

Position ID: w24TgwDsOcEDCA
Match ID: MAHyAAAAAAAA
It's 0-0 to 7.

Position 2

Position ID: Np7BATCwZ/ABMA
Match ID: cIn6AAAACAAA
Black leads 1-0 to 7

Position 3

Position ID: 4HPhQSDgc/ABMA
Match ID: cAn2ACAACAAA
White leads 2-1 to 7

Position 4

Position ID: cLfBCRCsPeAAIw
Match ID: cAn6ABAAGAAA
Black leads 3-1 to 7

Position 5

Position ID: WOeGAVC2bQVBQA
Match ID: QQk5AYAAMAAA
White leads 8-6 to 9
Both White and Black are on the bar and White owns the cube.

Brave enough to try these and give us your reasoning? Use that comments bit at the bottom, answers on Friday, until then enjoy the game.

A Reader Writes, Part 3.........

2011-07-27T04:44:00.000-07:00

Dear Dorbel, In the position below, I moved 23/14. It looks to me like this only leaves a hit by a 4 or a 65 and if I am missed I should get in easily. However, Gnu thinks that I should play 23/18, 6/2.

It looks as if I leave the checker back on the 18 it will be much more likely to be hit after my next roll, if opponent gets a checker out to my 7, 8 or 9pt. I cant see the advantage of staying back.

Thanks as always,

Position ID: s90AAg73nAcAEA
Match ID: 8Am2AAAAIAAA

It's the Crawford game in a five point match and Blue leads 4-0.

Yes I see what you mean.
"Only" a 4 and a 6-5 to hit is a lot of only, 17 shots or 47%. "If missed, should get in easily" is also questionable, as only 10 numbers (28%) get you home next turn. Sometimes it is right to take a direct shot when racing a straggler home, but these usually happen when your opponents home board is weak but about to get stronger, which doesn't apply here. Keeping the shots down with 23/18, 6/2 is clearly best. You may be able to hit something next turn to smooth your way home, or find a relatively safe point to land on. I agree that you may have to face more than 17 shots next turn, but you are just as likely to be facing the same or less or even none at all.
Your play is a small but clear error. If it left fewer shots or got you closer to home, it might be right.

Gnu's 2-ply analysis suggests that the two plays are very close (o.010), but a rollout shows that in fact 23/14 is an error costing 0.032. This translates to 52.4 game wins by staying back and 50.8 by running all the way. Can we draw a golden rule from this that stayng back has to be always best? Not really, reduce the shots and get the straggler closer to home, change the home boards a bit, any of these might make leaving the direct shot better or very close to equal. In the end, it's our old friend "pay now or pay later" and all you can do is add up what you risk and what you stand to gain by giving the shots straight away. If you do that and make a mistake, that's fine. It was probably, as here, a close decision anyway. If you fail to add up the hitting numbers and the number of rolls that get you home safely, then you will be making a guess and serve you right if you get it wrong. These crunch positions demand a lot of thought. Don't shirk it.

Have a look at this close relative to our starter position. How would you play 6-5 here?

Position ID: s90ABA73nAcAEA
Match ID: 8Im6AAAAIAAA

Taking the immediate risk with 23/12 is more attractive. It's only 16 shots, but much more importantly, Blue gets a lot closer to home. Now 20 numbers get him to safety next turn and this is just enough to tip the balance and make "pay now" the correct choice. It's very close though, the rollout makes that play best by just 0.009.

Thanks to A. Reader for the position. Until tomorrow, enjoy the game!

WIT FM, the Answers

2011-07-23T01:32:00.000-07:00

The commonly held view in backgammon is that the focus should be on checker play, because typically 75-80% of our errors occur in that area. My somewhat maverick view is that in fact concentrating on cube play and getting that right is more important. Why is this? For many years I'd observed that there were players in the chouettes and tournaments who made a lot of obvious errors in checker play, but survived and even prospered in the chouettes and did surprisingly well in the tournaments too. I could also see that there were very skilful players, mostly from the Middle East and the shores of the Mediterranean, who didn't get the results that their excellent checker play merited. It became obvious (to me) that the factor uniting these two groups was their cube play. The first group compensated for their checker weaknesses with a very accurate appreciation of the equity of positions, thus saving them from bad takes and enabling them to make efficient doubles. The second group, who had often been playing from childhood in a home where their father and their uncles took pride in skilful and subtle play, floundered badly with the cube, because it is to this day almost unknown in their home countries.
However, given that our bot analysis demonstrates clearly that most of our error rate is accumulated with the checkers, why does the cube matter so much? It works like this. Each match that we play is of course broken down into individual games. If the "luck" was more or less even in each game, then the most skilful player would win it, but this almost never happens. The usual dice in any individual game give one side or the other such an overwhelming advantage that it can't be overcome by skilful play, even if one side plays world class and the other side plays beginner! The better player's skill is swamped by the dice and the key skill in the great majority of games is to get the cube in the right place and at the right level.
So, does this mean that we need pay no attention to checker play? Not at all. There will occasionally be a game where the dice are even enough for the skill to count, notably the cubeless games as they have to be played to a finish and are thus longer than the others. There is also a great deal of skill in suiting your play to the position of the cube, notably in not overplaying a position and taking a bigger risk than needed in order to ship an efficient cube next turn.
Most of all though, checker play is important because the superior player will get the "luck" in a game more often than not. I had thought this for a long time and spent many hours trying to find the flaw in the argument, until finally a long thread on Fibsboard, illuminated by the contributions of boomslang, pck and Zorba among others demonstrated that this clearly was so and why.
http://www.fibsboard.com/fibsboard-forum-matches/how-do-%27luck%27-calculations-work/?all
Read it and marvel.

So now, when looking at the games of an individual, I concentrate first of all on their cube action and here are the positions from the last post and what I wrote about them at the time.

Position 1

Black on roll, first game of a 5 point match.
He doubled and I commented, "You doubled this and I can sort of see why. You lead in the race, your position is clearly better (one back against three, stronger board, outfield control) and you do have some threats but I think it is very important to see whether those threats lose your market and by how much. Over the board I would say, “Well if I can jump out and she does nothing special, it might be a pass, maybe not, but I’m not even a favourite to escape. I like to wait and see.” Basically, White is anchored, all her checkers are in play and the situation isn’t very volatile, so trivially easy take. Everybody takes this. The next sequence was Black 4-1, 11/7, 8/7, pretty good and White rolled 5-1, correctly played 24/23, 8/3*, but pretty bad. Now it’s a very strong double, probably a close pass, ideal. You get a point with a pass and probably about 1.07 points with a take. Note though that the point is concrete, on the sheet and you get it without making another play. The 1.07 points is theoretical and you have to play well to get it against an opponent who owns the cube. I would be pleased to get a pass here and wouldn’t mind if I got a take, nice position to be in.

There are two other things that you need to note here. The game has a long way to go if played to a finish, so the cube is completely live, i.e. at its most valuable. Also, you can take a little deeper than usual in the first game of a five pointer, because the redouble is unusually powerful. There are several reasons for this which I am happy to write about if anybody wants to see that, but for now note that the player owning a 2 cube at the start of a five pointer can wreak havoc with an aggressive redouble".

Position 2

Black leads 2-0 and is on the bar. He doubled this and this is what I wrote for him.

"A very early double, a blunder and a very easy take for White. If it was White that led 2-0, this is a double all right, but for the leader it isn't. Why? Once you lead in a short match (or towards the end of a long one), then doubling positions where the threat is largely to win a gammon is counter productive. In this case, if you win a doubled gammon, then one of the extra points for the gammon is wasted. Not only that, but if White redoubles, you don't get anything for a gammon at all and in addition, you can only use use three of the four points on the cube! Lastly, this position is extremely volatile and hard to predict, the opposite of what you need for a double when leading. You want a fairly static position close to White's take point, a holding game or a race ideally, one where the recube isn't going to be scary."

Position 3

Black leads 2-0 to 5 and is on the bar. White is on roll and redoubles.

"Clear redouble for White, killing the cube, nullifying Black's gammons and activating White's gammons as match winners. A huge pass for Black, for all the reasons above. White has a better position and a race lead and attacking threats. For money, easy take for Black with the cube very much alive and fair gammon chances himself, here, get out now and play at 2-2. "

The volume that you need to explain all this is a short volume called "How To Play Tournament Backgammon", by Kit Woolsey and published by Gammon Press. Not a modern volume, but it clearly explains the hows, whys and wherefores of adapting your play to match scores. Essential reading.

That's enough for today. Until the next dorbel daily, enjoy the game!

What's In This For Me?

2011-07-22T01:39:00.001-07:00

In this post I want to take a look at some positions from a lesson with a fibster. This player, a relative newbie to bg, has a rating around the 1900 mark so clearly can play more than a bit. We're going to take a look at his cube action and today we'll just have a look at three positions from a five point match and see how you cope with them as a quiz.

Position 1

Position ID: 4LsHACawzyMDCA
Match ID: cAmgAAAAAAAA

0-0 to 5. Black is on roll. What's the correct cube action for both sides?

Position 2

Position ID: kevBARTg28EYQA
Match ID: cAmgAAAAEAAA

Black leads 2-0 to 5. He is on the bar and on roll. Cube action for both sides?

Position 3

Position ID: 4NuJAUgx14MBFA
Match ID: ARmgAAAAEAAA
Black leads 2-0 to 5

Black is on the bar and White is on roll and owns a 2 cube. What is the correct cube action for both sides?

There you go. Favour us with your answers and much more importantly, your reasoning please.
I'll be back soon with the answers so don't delay!
Until then, enjoy the game!

Which Point Should I Clear?

2011-07-20T00:41:00.000-07:00

I promised you some cube positions from a private lesson today, but I just want to polish those a bit before putting them in the window, so here's a nice position from a Dutch reader. It's a money game, how should Black play 5-4?

Actually, the first thing to note about this position is that for money, Black should have doubled before this roll and presumably for several rolls before that, because money games are invariably played with the Jacoby rule, which states that you can't win a gammon unless there has been a cube turn. This is a huge pass, so Double/Drop. What about for match play? Curiously this is a very valuable match play reference position, where Black's equity is 1 point whether he cashes now or plays on for a gammon. As doubling secures the point for certain and playing on is worth a theoretical point that will require some skill to acquire, then to me, doubling is clearly correct. Worth remembering this one.
Now to the play. Lucas, playing Black here argues strongly for 7/3, 7/2. His reasoning is that he doesn't want to clear the 7pt later against direct contact with the anchor. If he plays 8/3, 8/4 he can see that 6-5, 6-4 and 6-3 next turn will leave a direct shot and that even if that is missed he has lots of bad sixes next turn as well. It's worthwhile to quantify the immediate risk to start with. 6/36 shot numbers multiplied by 11/36 hits equals 66/1296, a 5% chance of being hit in other words. Obviously playing 7/2, 7/3 reduces this "next turn" risk even further, but it does bury two checkers deep in the board, increasing the likelihood of leaving shots later when Black has to clear his stripped high points. In other words, clearing the 7pt first is less immediate risk and more later risk and as it happens, the two balance out almost exactly! It doesn't really matter which you play.

A subsidiary question. If Black plays 8/3, 8/4 and then on his next turn leaves a shot on the bar which White hits, can White double (or redouble) while she still has a checker behind Black's five prime? It depends on how much time White has left in which to throw the escaping 6.

It might look like this, if Black cleared the 8pt, White threw 6-4, Black left a shot and got hit with another 6-4. This is exactly a marginal take/pass so more timing for White, Black should pass, less timing and Black can eke out a take. It's much the same for a recube if White owns it. I assume the start of a longish match, but of course scores may radically affect either decision. Again, an excellent reference position to remember. If your brain works in that way, you might like to collect these two and start a collection for revision sessions.
Nice position, thanks Lucas. I quite like this close focus on a single position, rather than looking at three or four at once. Is this better for you too? Let me know, feedback is always appreciated, even if negative.
Until tomorrow, always a notional concept in this blog, enjoy the game!

Answers and More Questions.

2011-07-19T00:40:00.000-07:00

Position ID: 4PPgAWAzTvABMA
Match ID: cAkgAQAAAAAA

Here's Position One again. Black isn't too good to double because he doesn't have enough men in the zone to threaten a quick closeout. He must double now though, to avoid a joker sequence and this is a big pass for White. Playing on for a gammon is an error, if an understandable one, but taking is awful, a double blunder. If you voted to take this, then I suggest that you play it out 100 times with the cube on your side and disabuse yourself of the notion for ever. White will win this about 31% of the time, but lose about 40% gammons.

Position ID: 4HPkQUAzTvABMA
Match ID: cAkgAQAAAAAA

Here's Position 2, same sort of thing but now only one checker on the roof. This one is also double and pass. Again Black is momentarily short of builders, but more are arriving on the next bus and White gets gammoned too often to take. Periodically, there is a movement to claim this as a take, indeed some people do take it in practice, as does Gnu 2-ply, but it's wrong in my opinion, based on several long rollouts. Compared to Position One, White wins this one about 33% and loses about 39% gammons.
In both of these I attached a score of 0-0 to 9, but note that when trailing in a longish match these can quickly become viable takes for White. If she can make a high anchor in the next couple of moves, an aggressive redouble to 4 can net a surprising number of gammons of her own. Even in a five pointer, you can take position one quite easily if you trail 2-0. Not only does Black waste one of the two extra points that he wins with a gammon, but White's aggressive redouble eliminates all Black's gammons and even wastes one of the points for his plain win.
Those of you who like to research these things might like to make a little table of correct cube actions after an early 5-5/dance sequence. I could do it for you, but you won't remember it. Do it yourself though and you just might.

Position ID: 4HPwCSCwZ/ABMA
Match ID: cAmgADAACAAA

Now here's position 3, with Black on roll at the famous 4-away, 2-away score. You can double almost anything with a sniff of gammon at this score, because it kills the cube and the gammon threat is one way. So, this is a double and it is takeable. So close is this to a pass though, that the slightly inferior White play of 24/18, 13/10 with her opening 6-3 is a pass. How important is that? Not very. You'll probably meet this exact scenario five times in 25 years of bg and making the correct decision gains you at most an extra 0.2% match winning chances when it does occur each time.

Position 4 was the same position as above with Black trailing 2-away, 1-away Post Crawford. Black should play on for a gammon for the moment, but remain alert to doubling. If his gammon chances drop a lot and/or White gets to a position where she might become favourite, double/pass will be correct. For example, if from here Black rolls 3-3 and plays 13/10*(2), 6/3(2) and White then rolls 4-3 and anchors, then the double is probably correct. If White anchors lower down, it's probably right to keep going for the gammon. You can see that the playing on strategy, while clearly correct, does require a lot of good judgment, so if you think that this is beyond you, then taking your point now and going into the last game might be a good idea. It's an error, but not a large one. Too good to double/pass.

In the next post I want to show you some doubling positions from a private lesson. Easily the most common fault among players from novice to advanced is missing doubling opportunities, so I'll show you some of those and what we should be looking for to make the most of chances to up the stakes. That'll be tomorrow with any luck, so check back and until then, enjoy the game!

"A Reader Asks.......Part 2"

2011-07-16T03:23:00.000-07:00

As a follow-up to the last post, I now have the whole match from which that position came and here is the same game three rolls earlier. Thank you to Warner Bouzek who sent it to me. Feel free to do the same if you have something interesting.

Position ID: /10AABiz3QYQAg
Match ID: QQmpAAAAAAAA

Here is an excellent opportunity for a trap play. The best play is 20/18, 16/14, 7/3. Note how the moves to 18 and 14 cover every point in the outfield, ensuring a direct shot or its eqivalent after every five or six for White. Even if White rolls 5-1 or 5-2 and picks up her inboard blot, Black will still have 17 shots at the White checker on the deuce point including 6-6 and 4-4 from the 14pt. Even when White rolls 5-5 and covers the blot, Black still has 15 shots from the bar.
Some players will jib at the risk involved, unwilling to let White out in order to pursue a closeout and a gammon. Experts won't, because they have been here before. If you instinctively make the "safe" play here, then you won't know what happens after the trap play and you'll never learn to play it. You can avoid this by playing it fifty times and comparing the results with fifty rounds of your safe play. You'll soon grow to love the trap!

Another reader writes, "How early in the game should I think about doubling?" The answer is that you should always be alert to a double opportunity, as they can occur from the second roll onwards. Here are four examples. Take a look at them and let us know in the comments section what you would do with these. In each case Black is on roll. I want to know the correct cube action for both sides.

Position One

It's a nine point match, the first game and White opened with a 5-2, played 24/22, 13/8 and Black pounded her with 5-5. White danced. Should Black double and if he does, should White take?
Position 2

Again, nine point match, White rolled 6-2 and played 24/18, 13/11 and again, Black rolled 5-5 and again poor old White danced. Should Black double and should White take if he does?

Position 3

This is from a 5 point match and White leads 3-1. Black started with a 3-1 and White rolled a 6-3, correctly played 24/15. Should Black double and should White take if he does?

Position 4

The same position but now White leads 4-3 to 5 and it is post-Crawford. Should Black double and if he does, should White take?

Some of my expert readers will look at these and say, "Well these are too easy". However, they are all from live matches, all involving players at the top of the tree and all drew mistakes from one side or the other! See if you can do better please.

Until tomorrow, which may even be tomorrow, enjoy the game!

"A Reader Asks............."

2011-07-15T00:34:00.000-07:00

A reader sent me this position from a recent match and asked, "Why does the bot want me to break the bar point here? It thinks I should have broken it on the two preceding rolls as well. Surely I need to keep the last two White checkers contained?

It's 0-0 to 3 and White has the cube in the position below.

Position ID: /x8AABhzux0AAA
Match ID: QQlpAAAAAAAA

In this position it is correct to play 7/3, 7/5(2), getting ready to start the bearoff next turn and allowing White to exit with fives. This is good enough to make Black a 93% favourite in the game and about 7 of those will be match winning gammons. It is often right to keep the prime if White still has a good board and you want to force her to break it with fives, but with this roll you wouldn't do that anyway. You would have to play 7/1, 5/3 leaving you horribly stripped and vulnerable to leaving a shot, perhaps even a double shot.
A third alternative that becomes viable when White's board is fatally crashed, down to 3pts or fewer, is the trap play. Here that would be 7/1, 7/5, deliberately leaving a blot that White will be forced to hit with a five. The idea is that if White does hit, you can recirculate the hit checker, attacking the blot on the 2pt and hoping to close out two checkers for a gammon. It's not right with this roll, because Black's spares are poorly placed, but with a roll of 3-1 for example, it's well worth a try.

Position ID: /x8AABhzux0AAA
Match ID: QYlsAAAAAAAA

After 7/6, 7/4 you can see that if hit, Black will have ones, twos, threes and fours to hit back from the bar, a total of 31 shots. If White can't hit or has to leave with a six, then Black's checkers are ideally placed for an attack or to start the bearoff as the dice dictate. This play will lose at worst 1 game compared to the safe play, but will win about 8 extra gammons, which is good action.
Perhaps this reader was deceived by the pipcount, which shows White leading 59-67 before the roll. This is very misleading, because if it comes to a race, White will waste tons of pips bearing all those checkers off the ace point. A more accurate White pipcount allowing for that wastage would be about 100. How did I do that? You need to use the Effective Pip Count, developed by the late Walter Trice for just this sort of position. I could explain it to you, but if youare interested (and you should be because it is very, very useful) then go to http://www.bkgm.com/articles/EffectivePipCount/ and read it for yourself. Then read it again, however many times it takes to settle into your brain. It's priceless.

Got any positions you want to ask about? I'm easy enough to find on Fibs or GridGammon, or if you like use the comment form at the end of each post and include a Gnu ID. I'll be happy to give you my opinion.
Enjoy the Game!

Books and Magazines

2011-07-13T11:35:00.000-07:00

I am often asked to recommend books. I invariably suggest "Backgammon Boot Camp" by the late Walter Trice. Walter wrote a series of articles for the online magazine GammonVillage under the title Beginner's Boot Camp, taking everybody through the basic techniques in beautifully written, clear and accurate lessons, embracing quite advanced concepts along the way. Even if you feel that anything with beginner in the title is not for you, believe me this book is still essential reading. As far as I am aware, these articles are still on GammonVillage, so you may prefer to buy a Gold subscription and get the lot plus a huge archive of great articles by Jacobs, Zare, Hickey, Sax and others, plus annotated matches, news, terrific value.
Generally speaking, books written thirty or more years ago are only of historical interest, but from that time "Backgammon" by Paul Magriel is still brilliant, although probably worth getting the 2004 reissue. Anything from then by Danny Kleinman is great reading, entertaining and thought provoking, particularly "Vision Laughs At Counting". Bill Robertie is probably the most prolific author, although the quality of his work varies a lot. His "ModernBackgammon" is an excellent work for the advanced player and it includes a 25 point annotated match between Jerry Grandell and Nack Ballard, worth the cover price on its own.
"How to Play Tournament Backgammon" by Kit Woolsey is a fairly short book, but essential if you want to understand how to tailor your play to match scores.
Finally, in this anything but comprehensive list, a cheapy worth ten times its cover price is "100 Backgammon Puzzles" by Paul Lamford. The choice of positions is excellent and from each Paul draws a neat little conclusion that will help you when you meet something similar along the way.

Perhaps the worst ever book is "Backgammon For Blood" by Bruce Becker, a complete guide to playing like a bozo and losing all your money quickly. It was apparently Dubya's favourite and is hilariously entertaing, without meaning to be. Do not confuse this with the book of the same title by Chris Bray, which like all Chris's writing is entertaining and useful. His publisher chose the title without telling him!

All of these are available new and used from various outlets on the net, search around, have fun and build up a little collection. I recently found on ebay a copy of "Complete Backgammon" by Walter L. Richard, 1931, with dustjacket, signed by the author and dedicated to Harold Thorne, also a writer of that period. I hope that you will be as lucky.
Until the next time, enjoy the game!

the dorbel daily

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