Backgammon Brain Busters #68

by Michael Strato
14 March 2006

Strategy Talk

Players of all levels are invited to share their view on these interesting positions that we came across while honing our backgammon skills in match play.

Is the computer program always right? As we have seen in the past, even the best programs get certain scenarios wrong while world class human players have a better grasp of these situations through the experience of years of play.

The "Brain Busters" series offers three new backgammon positions in each article, problems that we believe to be challenging and worthy of thought and discussion - please post your opinion on how you would play these positions in the forum thread below.

We will do their rollouts with Snowie 4 Pro and publish the results along with a new set of positions about once a week. Enjoy!

Note: See the rollouts results of all previous Brain Busters articles at this link.

Please give us your thoughts on these without the help of a bot.

Position 1:


		Pip: 142
		7 point match Green-White: Score 0-0
		Pip: 145

Position 2:


		Pip: 150
		7 point match Green-White: Score 5-2
		Pip: 176

Position 3: Green on roll, cube action?


		Pip: 127
		5 point match Green-White: Score 0-0
		Pip: 122

WARNING! - ROLLOUTS

March 21, 2006: Here are the Snowie rollouts for the three positions above:

Position 1:


		Pip: 142
		7 point match Green-White: Score 0-0
		Pip: 145

#		Ply	Move	Equity
	1	R	13/9 2/1*	-0.276
			0.3% 12.0% 45.7% 54.3% 22.9% 1.0%
			95% confidence interval: - money cubeless eq.: -0.201 ±0.037. Rollout settings: Full rollout, 144 games (equiv. 5222 games), played 3-ply (precise), random seed, with race database.
	2	R	9/5 6/5	-0.425 (-0.149)
			0.8% 13.8% 43.7% 56.3% 30.5% 1.2%
			95% confidence interval: - money cubeless eq.: -0.296 ±0.049. Rollout settings: Full rollout, 144 games (equiv. 4033 games), played 3-ply (precise), random seed, with race database.
	3	R	9/8 6/2	-0.535 (-0.259)
			0.4% 10.5% 41.1% 58.9% 29.2% 0.7%
			95% confidence interval: - money cubeless eq.: -0.368 ±0.035. Rollout settings: Full rollout, 144 games (equiv. 5688 games), played 3-ply (precise), random seed, with race database.
	4	3	13/8	-0.429 (-0.152)
			0.6% 11.7% 42.8% 57.2% 28.7% 1.4%
			Speed Parameter: Precise.
	5	3	6/2 3/2	-0.525 (-0.249)
			0.4% 9.8% 40.3% 59.7% 26.1% 0.9%
			Speed Parameter: Fast.

Position 2:


		Pip: 150
		7 point match Green-White: Score 5-2
		Pip: 176

#		Ply	Move	Equity
	1	R	13/7(2) 11/5*(2)	0.608
			1.3% 29.5% 66.8% 33.2% 7.5% 0.6%
			95% confidence interval: - money cubeless eq.: 0.563 ±0.028. Rollout settings: Full rollout, 288 games (equiv. 8498 games), played 3-ply (precise), random seed, with race database.
	2	R	11/5*(2) 8/2(2)	0.588 (-0.020)
			1.1% 32.7% 64.1% 35.9% 7.6% 0.5%
			95% confidence interval: - money cubeless eq.: 0.539 ±0.025. Rollout settings: Full rollout, 288 games (equiv. 10253 games), played 3-ply (precise), random seed, with race database.
	3	R	24/18(2) 11/5*(2)	0.569 (-0.039)
			0.7% 24.4% 66.8% 33.2% 6.0% 0.2%
			95% confidence interval: - money cubeless eq.: 0.525 ±0.024. Rollout settings: Full rollout, 288 games (equiv. 9589 games), played 3-ply (precise), random seed, with race database.
	4	R	24/18 13/7 11/5*(2)	0.460 (-0.148)
			0.4% 25.1% 64.7% 35.3% 7.9% 1.0%
			95% confidence interval: - money cubeless eq.: 0.460 ±0.046. Rollout settings: Full rollout, 144 games (equiv. 3881 games), played 3-ply (precise), random seed, with race database.
	5	3	24/18 11/5*(2) 8/2	0.240 (-0.368)
			1.1% 23.7% 58.5% 41.5% 10.7% 0.7%
			Speed Parameter: Fast.

Position 3: Green on roll, cube action?


		Pip: 127
		5 point match Green-White: Score 0-0
		Pip: 122

Cube action equity
Rollout	Money equity:	0.824
	2.3% 46.9% 71.4% 28.6% 9.2% 0.4%
	95% confidence interval: - money cubeless eq.: 0.824 ±0.017, - live cube no redouble: 1.077 ±0.022, - live cube redouble take: 1.286 ±0.037. Rollout settings: Full rollout, 648 games (equiv. 23785 games), played 3-ply (precise), cube 3-ply, random seed, with race database.
Evaluations
1.	No redouble	1.058
2.	Redouble, pass	1.000	(-0.058)
3.	Redouble, take	1.299	(+0.241)
Proper cube action: Too good to redouble, pass			19%
Live cube
1.	No redouble	1.077
2.	Redouble, pass	1.000	(-0.077)
3.	Redouble, take	1.286	(+0.209)
Proper cube action: Too good to redouble, pass			27%

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Subject: Re: Backgammon Brain Busters #68

From: jk_ace

Date: 17 Mar 2006 10:40 EST

1) 9/5, 6/5. Close between 3 plays. 9/5, 6/5 will pay off longterm - unless we spend the rest of the game trying to come in and this play leaves the most returns. 13/9, 2/1* puts white on the bar and gives us some flexibility and duplicates 1s but does nothing to improve our board. But white's stripped position means he'll often have to leave another blot or 2. The ugly 9/8, 6/2 leaves only one extra blot which could be very important against whites 4 pt board and makes another home board point but leaves more 15 hits and gives up a good blocking point. Whites lack of direct attackers on the 2 point swing it to making the 5 point for me.

2) 11/5*(2), 24/18, 13/7. After the obvious first 2 we can make either bar point or start both. 8/2(2) is also a possibility. With our much better board we need to go all out to pick up white's 2nd blot and starting both bar points having threats on both sides of the board is the best way to do this.

3) ND/T. Many of our wins will be gammons so a 4 cube has a lot of wastage - not worth giving away the cube. May be a double from the center.

Subject: Re: Backgammon Brain Busters #68

From: StarLight

Date: 18 Mar 2006 06:59 EST

1. 9/5 6/5 a la JK I do not find it close at all! 1. White has already buried 2 stones on the home ace point. 2. White has no spares anywhere, so shots are coming, and there is no ammo to attack blots in white's home board. 3. Many 6s are awkward for white, so now is the time to lock the famous 5 point.

2. At this score there is only one play: 11/5 x 2 (zzzzzzzzzzzzzzzzzzzzzzzzzz) 13/7 x 2 a. This isolates white's runner, and builds a 5 prime. b. No other play is so unwelcome by white. And white's 6s STINK! c.The gammon possibility is now very high, as white's LONE runner can never anchor. The second white blot can be picked off, but the GAMMON wins the match..

3.D/Drop With 2 more fat targets, and an inferior to green board, white must drop the cheap 1 point.

Starlight, out!

Subject: Re: Backgammon Brain Busters #68

From: SvempaSnake

Date: 21 Mar 2006 11:17 EST

1. I see only 13/8! ( I didn't see 9/5, 6/5 :-( but now when I see it I still don't make it. ) 13/8 leaves virtually only one blot instead of two when making the 5 point. The 9 point itself is very nice here too.

2. 11/5(2) is easy. Priming with 13/7(2) looks tempting but I prefer the calm and easy 24/18(2). Looks likely that I can double out (or double in) my opponent soon after this move.

3. Tricky. My guess is ND/P. I would go for No Double (hoping for gammon, and also keeping my option to double later on). From whites side it's also tricky. Might be a take since gammons won't cost much extra with a 4- cube. "Only" 11/36 rolls that hits a second guy directly. Anyway I would chicken out and pass to 0-2 as white.

Sven-Olav Norén

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