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A surprising (to me) save-the-gammon play

Posted By: David Rockwell
Date: Thursday, 17 December 2015, at 5:09 a.m.

In Response To: A surprising (to me) save-the-gammon play (David Levy)

This theme occurs frequently when rolling threes with several checkers on the eight point. When is it right to waste a pip before you must? In the original position, you will waste pips clearing the ten point unless you roll four twice. This can happen. But, there's a good chance it won't. After playing 13-8, you will waste pips on all fives and sixes. Also relevant is that after keeping the checker on the 13, a subsequent six followed by an ace avoids the misses that everyone noticed. The back checker gives you more flexibility in playing large numbers. We waste a pip now that we're likely to waste later anyway.

Try to visualize the idea with this position. You probably won't roll two deuces. So, you waste one pip now with a three rather than risking wasting more later. A three played from the eight is a relatively efficient crossover in this position. Look at a roll of 54 next in both positions.

 White is Player 2 score: 0 pip: 8 Unlimited GameJacoby Beaver pip: 78 score: 0 Blue is Player 1
XGID=-BBBBBB-B-----------A--cb-:1:1:1:53:0:0:3:0:10
Blue to play 53

1.Rollout120/15 8/5eq: -1.5334
 Player:Opponent: 0.00% (G:0.00% B:0.00%)100.00% (G:53.34% B:0.00%) Conf.: ±0.0001 (-1.5335...-1.5333) - [100.0%]Duration: 0.1 second
2.Rollout120/12eq: -1.6025 (-0.0691)
 Player:Opponent: 0.00% (G:0.00% B:0.00%)100.00% (G:60.25% B:0.00%) Conf.: ±0.0001 (-1.6026...-1.6023) - [0.0%]Duration: 0.1 second
1 5184 Games rolled with Variance Reduction.
Dice Seed: 97350134
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.10

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