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Prime vs Blitz: 1 Checker Removed Behind a 5 Prime

by Ash Dalvi
17 July 2012

Ash Dalvi

In my final article on Prime vs Blitz, I look at situations when white has one checker behind (but not at the edge) of his opponent's 5 prime and black has a 1 or 2 checkers on the bar.

At the end of this article, I will present a list of numbers that can be memorised in order to calculate Prime vs Blitz cubes.

Standard Reference Positions

Throughout this series of articles on Prime vs Blitz, I have started with reference positions in which black's prime starts from his 5 pt. For consistency, I will do the same here.

The Count

The counting method will be the same as that employed in earlier Prime vs Blitz articles. If you are not sure how the counting method works, please refer to my previous articles.

In Position 1, count 1 for each white checker that has made a board point or is threatening to make a board point and 0.5 for any others in white's outfield. As such, the 9 checkers between the 3 and 6 pt count as 1 each, while the checker on the 11 pt counts as 0.5. This basic count of 9.5 assumes that white has a 3 pt board. Previous articles indicate that we need to add 2 for white's 4 pt board and 0.5 for the checker in white's outfield that cannot make a board pt. Furthermore, the extra black checker on his 24 pt has consistently counted as 1.

Position 1: First Cube = Count of 12.5

is Player 2

score: 0
pip: 158

11 point match

pip: 129
score: 0

is Player 1

XGID=aa-BBBC----AcD--bbbbb---A-:0:0:1:00:0:0:0:11:10

on roll, cube action?

Analyzed in Rollout
No Double
Player Winning Chances:	61.13% (G: 32.46% B: 1.09%)
Opponent Winning Chances:	38.87% (G: 7.07% B: 0.33%)
Double/Take
Player Winning Chances:	61.54% (G: 32.41% B: 1.08%)
Opponent Winning Chances:	38.46% (G: 6.95% B: 0.31%)

Cubeless Equities
No Double:	+0.489
Double:	+1.018

Cubeful Equities
No Double:	+0.660 (-0.026)
Double/Take:	+0.685
Double/Drop:	+1.000 (+0.315)

Best Cube action: Double / Take

Rollout details
1296 Games rolled with Variance Reduction. Dice Seed: 68680035 Moves: 3 ply, cube decisions: XG Roller

Confidence No Double:	± 0.019 (+0.641...+0.678)
Confidence Double:	± 0.024 (+0.661...+0.710)

Double Decision confidence:	95.0%
Take Decision confidence:	100.0%

Duration: 19 minutes 45 seconds