the dorbel daily

Wednesday 28 September 2011

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.

Just Whack It.

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!

Monday 19 September 2011

Make Mine A Double Answers.

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!

Saturday 17 September 2011

Make Mine A Double

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!

Tuesday 13 September 2011

Free Sample Answers.

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!

Saturday 10 September 2011

Free Samples.

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!

Thursday 1 September 2011

Mochy v. Falafel

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.