My Play Would Have Won A Gammon

by Gerry Tansey

That’s what I imagine some armchair quarterback would have said to me if he or she had seen this sequence from a recent sparring session I had with XG.  I was trailing 6-4 in a match to 11, but this game was going swimmingly.  First, I offered a double in the following position:

Tansey1

I’ll talk a little bit about this double at the end of the article.  After XG took the cube, I rolled a suboptimal 53, which I played 13/5.  XG also rolled 53, which was a considerably better roll for the bot.  XG brought one checker to safety and threatened to escape the other, playing 23/18, 16/13.  I was under severe pressure to hit the straggler.

Tansey2

I was under severe pressure to hit the straggler, but I did with a nice 63, bringing down more ammunition with 13/10 13/7*.  I soon filled in the 4-point, and a couple of turns later, I had this 62 to play:

Tansey3

I really didn’t spend too much time on this play.  I ran the back checker, but before clicking on my dice to end my turn, I did think, “Hey, that closes the board too.  Whatever.  We’ll do that later.”

Well, you don’t have to know what “hubris” means to have an inkling of what happened next.  XG rolled 25 from the bar, squirting out to the bar point.  I rolled a 64 (which would have escaped the back man had I closed the board), and had to settle for winning a single game.

In a live tournament match, this kind of sequence can have a negative psychological effect.  The naysayers in your mind may harp on you relentlessly, saying things like, “We just tossed two points down the drain.  What were you afraid of?  His prime had two holes in it.  We could have escaped easily. This is backgammon.  The dice are capricious enough.  We can’t afford to just give points away.”

But remember, the plural of “anecdote” is not “data.”  There will almost always be sequences of rolls that punish the play you made and reward the play you didn’t.  And the fact is that in this case, White does not have much time to escape Black’s blockade if he doesn’t do it now.  Any roll that does not contain a 2 or a 4 (16 numbers) makes no progress, and the board cracks immediately on 65 and 55.  Further, after a number like 52, White still may bust his board before he escapes.  It is easy to see sequences where White fails to escape and thus loses the game.

And in reality, if White uses the 62 to escape, most of the time he can then close Black out later.  Usually Black fans, and most of Black’s entering numbers lead to his being pounded relentlessly.  Yes, 42 and 22 hit, but White often hit back from the roof, and White’s advantage in home board points usually leads to an easy victory, and often a gammon.

A rollout shows that the plays are not close.  Closing the board is a big blunder, losing 6.8% more games, while winning only 1.5% more gammons, than escaping.

1.Rollout1	24/16	eq: +1.380 	Player: Opponent:	90.58% (G:53.78% B:0.10%) 9.42% (G:0.87% B:0.09%)	Conf.: ± 0.005 (+1.375...+1.385) - [100.0%] Duration: 2 minutes 19 seconds 2.	Rollout1	8/2 4/2	eq: +1.231 (-0.149) 	Player: Opponent:	83.83% (G:55.25% B:0.07%) 16.17% (G:1.34% B:0.05%)	Conf.: ± 0.006 (+1.225...+1.237) - [0.0%] Duration: 2 minutes 24 seconds   1 1296 Games rolled with Variance Reduction. Moves: 3-ply, cube decisions: XG Roller

1. Rollout1 24/16 eq: +1.380
Player:
Opponent: 90.58% (G:53.78% B:0.10%)
9.42% (G:0.87% B:0.09%) Conf.: ± 0.005 (+1.375…+1.385) – [100.0%]
Duration: 2 minutes 19 seconds
2. Rollout1 8/2 4/2 eq: +1.231 (-0.149)
Player:
Opponent: 83.83% (G:55.25% B:0.07%)
16.17% (G:1.34% B:0.05%) Conf.: ± 0.006 (+1.225…+1.237) – [0.0%]
Duration: 2 minutes 24 seconds
1 1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller

Now, as promised, I’ll discuss the cube mentioned at the start of this article.  Here is a rollout:

Analyzed in RolloutNo double	Double/Take   Player Winning Chances:	61.34% (G:31.93% B:0.50%)	61.46% (G:33.62% B:0.51%)   Opponent Winning Chances:	38.66% (G:9.51% B:0.46%)	38.54% (G:10.01% B:0.53%)   Cubeless Equities	+0.456	+1.016 Cubeful Equities      No double:	+0.610 (-0.234)	±0.012 (+0.598..+0.621)   Double/Take:	+0.844	±0.015 (+0.829..+0.859)      Double/Pass:	+1.000 (+0.156)   Best Cube action: Double / Take Rollout details 1296 Games rolled with Variance Reduction. Moves: 3-ply, cube decisions: XG Roller   Double Decision confidence:	100.0% Take Decision confidence:	100.0% Duration: 11 minutes 35 seconds

Analyzed in Rollout No double Double/Take
Player Winning Chances: 61.34% (G:31.93% B:0.50%) 61.46% (G:33.62% B:0.51%)
Opponent Winning Chances: 38.66% (G:9.51% B:0.46%) 38.54% (G:10.01% B:0.53%)
Cubeless Equities +0.456 +1.016
Cubeful Equities
No double: +0.610 (-0.234) ±0.012 (+0.598..+0.621)
Double/Take: +0.844 ±0.015 (+0.829..+0.859)
Double/Pass: +1.000 (+0.156)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence: 100.0%
Take Decision confidence: 100.0%
Duration: 11 minutes 35 seconds

It’s a huge double and a big take.  White has a modest racing lead, a better board, and threats to hit Black’s blots.  Any hit-fan sequence is a huge market loss.  Black certainly has enough chances to take, though.  Sometimes White fails to hit Black, sometimes White hits the 9-point checker and Black anchors, sometimes White hits loose with a 6 and Black hits back.  Black is doing fine in all these sequences.

The score matters a little bit here.  At the score, Black will have to wait a long time before he can give a correct redouble, and if the position is gammonish, that redouble may never be right.  As a result, White should be a bit more eager to use the cube at the score, as Black’s redoubling potential is severely limited.  That being said, for money the correct decisions are the same, and they’re still not close.

Analyzed in RolloutNo double	Double/Take   Player Winning Chances:	61.49% (G:31.03% B:0.55%)	61.72% (G:32.44% B:0.52%)   Opponent Winning Chances:	38.51% (G:8.93% B:0.44%)	38.28% (G:9.55% B:0.49%)   Cubeless Equities	+0.452	+0.927 Cubeful Equities No double:	+0.514 (-0.121)	±0.010 (+0.504..+0.523) Double/Take:	+0.635	±0.016 (+0.619..+0.651) Double/Pass:	+1.000 (+0.365)   Best Cube action: Double / Take Rollout details 1296 Games rolled with Variance Reduction. Moves: 3-ply, cube decisions: XG Roller   Double Decision confidence:	100.0% Take Decision confidence:	100.0% Duration: 9 minutes 16 seconds

Analyzed in Rollout No double Double/Take
Player Winning Chances: 61.49% (G:31.03% B:0.55%) 61.72% (G:32.44% B:0.52%)
Opponent Winning Chances: 38.51% (G:8.93% B:0.44%) 38.28% (G:9.55% B:0.49%)
Cubeless Equities +0.452 +0.927
Cubeful Equities
No double: +0.514 (-0.121) ±0.010 (+0.504..+0.523)
Double/Take: +0.635 ±0.016 (+0.619..+0.651)
Double/Pass: +1.000 (+0.365)
Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller
Double Decision confidence: 100.0%
Take Decision confidence: 100.0%
Duration: 9 minutes 16 seconds

The double goes from “huge” to merely “big,” while the take goes from “big” to “monster.”  A lot can happen in the next couple of rolls, and often one side is not going to be very happy.  This volatility is the heart and soul of backgammon.  Relish it.

And by the way, I do realize that I just showed you a game where I did everything right.  It does happen every once in a while.  I promise I’ll show you a screw-up next time.

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