Backgammon Brain Busters #61

by Michael Strato
24 January 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.

NOTE: We would like to hear your personal observations alone, so please do not use a program to check these positions.

Position 1:


		Pip: 145
		7 point match Green-White: Score 6-2
		Pip: 122

Position 2:


		Pip: 162
		9 point match Green-White: Score 2-6
		Pip: 122

Position 3: Green on roll, cube action?


		Pip: 59
		9 point match Green-White: Score 4-2
		Pip: 85

WARNING! - ROLLOUTS

January 31, 2006: Here are the Snowie rollouts for the three positions above:

Position 1:


		Pip: 145
		7 point match Green-White: Score 6-2
		Pip: 122

#		Ply	Move	Equity
	1	R	9/5(2) 8/4(2)	0.528
			0.5% 13.9% 78.1% 21.9% 2.3% 0.2%
			95% confidence interval: - money cubeless eq.: 0.680 ±0.024. Rollout settings: Full rollout, 144 games (equiv. 5315 games), played 3-ply (precise), random seed, with race database.
	2	R	9/5(2) 6/2(2)	0.512 (-0.016)
			0.5% 11.0% 76.9% 23.1% 2.0% 0.1%
			95% confidence interval: - money cubeless eq.: 0.632 ±0.020. Rollout settings: Full rollout, 144 games (equiv. 9968 games), played 3-ply (precise), random seed, with race database.
	3	R	8/4(2) 6/2(2)	0.510 (-0.019)
			0.4% 10.8% 77.1% 22.9% 2.7% 0.1%
			95% confidence interval: - money cubeless eq.: 0.627 ±0.019. Rollout settings: Full rollout, 144 games (equiv. 7576 games), played 3-ply (precise), random seed, with race database.
	4	R	13/5(2)	0.471 (-0.057)
			0.4% 11.8% 74.9% 25.1% 2.3% 0.0%
			95% confidence interval: - money cubeless eq.: 0.597 ±0.024. Rollout settings: Full rollout, 144 games (equiv. 7305 games), played 3-ply (precise), random seed, with race database.
	5	3	13/9 9/5(3)	0.450 (-0.078)
			0.8% 11.6% 74.5% 25.5% 3.2% 0.1%
			Speed Parameter: Precise.

Position 2:


		Pip: 162
		9 point match Green-White: Score 2-6
		Pip: 122

#		Ply	Move	Equity
	1	R	24/18 6/2*	1.507
			0.7% 71.1% 86.1% 13.9% 2.1% 0.2%
			95% confidence interval: - money cubeless eq.: 1.417 ±0.013. Rollout settings: Full rollout, 576 games (equiv. 20234 games), played 3-ply (precise), random seed, with race database.
	2	R	20/14 6/2*	1.503 (-0.004)
			0.6% 72.2% 85.8% 14.2% 2.9% 0.1%
			95% confidence interval: - money cubeless eq.: 1.416 ±0.014. Rollout settings: Full rollout, 576 games (equiv. 19913 games), played 3-ply (precise), random seed, with race database.
	3	R	10/4 6/2*	1.492 (-0.015)
			0.7% 71.1% 85.7% 14.3% 2.8% 0.1%
			95% confidence interval: - money cubeless eq.: 1.403 ±0.015. Rollout settings: Full rollout, 576 games (equiv. 16771 games), played 3-ply (precise), random seed, with race database.
	4	3	24/14	1.239 (-0.267)
			2.2% 56.9% 81.2% 18.8% 3.3% 0.2%
			Speed Parameter: Fast.
	5	3	24/18 24/20	1.187 (-0.320)
			1.8% 53.6% 80.6% 19.4% 3.1% 0.2%
			Speed Parameter: Fast.

Position 3: Green on roll, cube action?


		Pip: 59
		9 point match Green-White: Score 4-2
		Pip: 85

Cube action equity
Rollout	Money equity:	0.274
	0.1% 4.9% 62.1% 37.9% 1.8% 0.0%
	95% confidence interval: - money cubeless eq.: 0.274 ±0.009, - live cube no double: 0.255 ±0.015, - live cube double take: 0.150 ±0.027. Rollout settings: Full rollout, 648 games (equiv. 74120 games), played 3-ply (precise), cube 3-ply, random seed, with race database.
Evaluations
1.	No double	0.266
2.	Double, take	0.145	(-0.120)
3.	Double, pass	1.000	(+0.734)
Proper cube action: No double, take			14%
Live cube
1.	No double	0.255
2.	Double, take	0.150	(-0.106)
3.	Double, pass	1.000	(+0.745)
Proper cube action: No double, take			12%