Brain Busters #17

by Michael Strato
8 March 2005

Strategy Talk

Players of all levels are invited to share 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 results of the rollouts for our last three positions in:
"Brain Busters #16".

Position 1:


		Pip: 154
		7 point match Green-White: Score 0-0
		Pip: 156

Position 2:


		Pip: 161
		5 point match Green-White: Score 2-4
		Pip: 157

Position 3: Green on roll, cube action?


		Pip: 56
		11 point match Green-White: Score 2-1
		Pip: 128

WARNING! ROLLOUTS

March 15, 2005: Here are the Snowie rollouts for the three positions above:

Position 1:


		Pip: 154
		7 point match Green-White: Score 0-0
		Pip: 156

#		Ply	Move	Equity
	1	R	16/15 8/7(2) 6/5	0.270
			0.9% 15.0% 58.8% 41.2% 14.8% 0.9%
			95% confidence interval: - money cubeless eq.: 0.178 ±0.027. Rollout settings: Full rollout, 324 games (equiv. 8496 games), played 3-ply (precise), random seed, with race database.
	2	R	16/13 6/5	0.241 (-0.029)
			0.6% 13.4% 57.4% 42.6% 11.6% 0.6%
			95% confidence interval: - money cubeless eq.: 0.166 ±0.021. Rollout settings: Full rollout, 324 games (equiv. 12783 games), played 3-ply (precise), random seed, with race database.
	3	R	8/7(3) 6/5	0.199 (-0.070)
			1.0% 15.8% 56.3% 43.7% 15.1% 0.7%
			95% confidence interval: - money cubeless eq.: 0.136 ±0.028. Rollout settings: Full rollout, 324 games (equiv. 10142 games), played 3-ply (precise), random seed, with race database.
	4	3	11/10 8/7(2) 6/5	0.233 (-0.037)
			0.9% 17.0% 57.1% 42.9% 15.2% 0.9%
			Speed Parameter: Precise.
	5	3	24/23 8/7(2) 6/5	0.224 (-0.046)
			0.9% 16.0% 57.2% 42.8% 15.3% 0.8%
			Speed Parameter: Precise.

Position 2:


		Pip: 161
		5 point match Green-White: Score 2-4
		Pip: 157

#		Ply	Move	Equity
	1	R	bar/21 22/18* 8/4 6/2*	0.760
			1.4% 23.6% 63.1% 36.9% 7.9% 0.4%
			95% confidence interval: - money cubeless eq.: 0.428 ±0.025. Rollout settings: Full rollout, 324 games (equiv. 11031 games), played 3-ply (precise), random seed, with race database.
	2	R	bar/21 8/4 6/2*(2)	0.725 (-0.035)
			1.3% 24.2% 62.9% 37.1% 8.0% 0.2%
			95% confidence interval: - money cubeless eq.: 0.431 ±0.025. Rollout settings: Full rollout, 324 games (equiv. 9597 games), played 3-ply (precise), random seed, with race database.
	3	R	bar/21 22/18* 6/2*(2)	0.689 (-0.070)
			1.5% 22.6% 60.3% 39.7% 9.5% 0.3%
			95% confidence interval: - money cubeless eq.: 0.350 ±0.026. Rollout settings: Full rollout, 324 games (equiv. 10012 games), played 3-ply (precise), random seed, with race database.
	4	3	bar/21 22/18*/14 8/4	0.687 (-0.072)
			1.2% 20.3% 62.2% 37.8% 8.2% 0.3%
			Speed Parameter: Precise.
	5	3	bar/21 22/18* 13/9 8/4	0.645 (-0.114)
			1.2% 20.9% 60.1% 39.9% 9.0% 0.4%
			Speed Parameter: Precise.

Position 3: Green on roll, cube action?


		Pip: 56
		11 point match Green-White: Score 2-1
		Pip: 128

Cube action equity
Rollout	Money equity:	0.856
	0.8% 24.6% 82.5% 17.5% 4.8% 0.0%
	95% confidence interval: - money cubeless eq.: 0.856 ±0.011, - live cube no redouble: 1.038 ±0.013, - live cube redouble take: 1.641 ±0.025. Rollout settings: Full rollout, 1296 games (equiv. 37367 games), played 3-ply (precise), cube 3-ply, random seed, without race database.
Evaluations
1.	No redouble	1.027
2.	Redouble, pass	1.000	(-0.027)
3.	Redouble, take	1.595	(+0.568)
Proper cube action: Too good to redouble, pass			5%
Live cube
1.	No redouble	1.038
2.	Redouble, pass	1.000	(-0.038)
3.	Redouble, take	1.641	(+0.603)
Proper cube action: Too good to redouble, pass			6%