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Prime vs Blitz: 2 Checkers Behind a 5 Prime

by Ash Dalvi
20 June 2012

Ash Dalvi

In my penultimate article on Prime vs Blitz, I look at situations when you have 2 checkers behind your opponent's 5 prime and he has 1 or 2 checkers on the bar.

The aim of this series of articles is that each position-type will be associated with a pair of numbers.

The first number will represent the first cube position and the second number will signify first pass. By remembering these numbers and using a simple counting method, it should be possible to work out most variations of these positions.

Standard Reference Positions

In order to remain consistent with my previous 2 articles on Prime vs Blitz, I will begin with reference positions with black's prime starting from his 5 pt.

The Count

I will use the same counting method as I used in my previous Prime vs Blitz articles.

In Position 1, we count 1 for every 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. Therefore, the 11 checkers between the 4 and 8 pt count as 1 each, giving a total count of 11. This basic count assumes that white only has a 3 pt board. My previous Prime vs Blitz articles have shown that we need to add 2 to the count when white has a 4 pt board. In Position 1, white has a basic count of 11 plus 2 for the 4 pt board, giving a total count of 13. As the rollout for Position 1 is not statistically significant, this is a borderline first cube position when white is anchored on the 21 pt.

Position 1: First Cube = Count of 13

is Player 2

score: 0
pip: 147

11 point match

pip: 119
score: 0

is Player 1

XGID=a--BCCC-----dB--bbbbbB----:0:0:1:00:0:0:0:11:10

on roll, cube action?

Analyzed in Rollout
No Double
Player Winning Chances:	58.22% (G: 34.47% B: 0.21%)
Opponent Winning Chances:	41.78% (G: 6.62% B: 0.21%)
Double/Take
Player Winning Chances:	58.23% (G: 34.79% B: 0.23%)
Opponent Winning Chances:	41.77% (G: 6.71% B: 0.27%)

Cubeless Equities
No Double:	+0.448
Double:	+0.923

Cubeful Equities
No Double:	+0.520 (-0.011)
Double/Take:	+0.531
Double/Drop:	+1.000 (+0.469)

Best Cube action: Double / Take

Rollout details
5184 Games rolled with Variance Reduction. Dice Seed: 68680035 Moves: 3 ply, cube decisions: XG Roller

Confidence No Double:	± 0.012 (+0.508...+0.531)
Confidence Double:	± 0.013 (+0.518...+0.544)

Double Decision confidence:	89.5%
Take Decision confidence:	100.0%

Duration: 1 hour 18 minutes