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Antigammon puzzle SOLUTION

Posted By: Bob Koca
Date: Tuesday, 2 July 2024, at 3:06 p.m.

In Response To: Antigammon puzzle (Bob Koca)

Here are two:

1)

		White is Player 2 score: 0 pip: 46 1 point match pip: 86 score: 0 Blue is Player 1
XGID=-BBBC-C-A--A--------afccbA:0:0:1:53:0:0:0:1:10
Blue to play 53

1.	Rollout1	Bar/20* 8/5	eq: +0.379
	Player: Opponent: 68.93% (G:1.44% B:0.03%) 31.07% (G:8.58% B:0.18%) Conf.: ± 0.002 (+0.376...+0.381) - [100.0%] Duration: 53.3 seconds
2.	Rollout1	Bar/20* 20/17	eq: +0.365 (-0.014)
	Player: Opponent: 68.24% (G:0.95% B:0.03%) 31.76% (G:1.87% B:0.00%) Conf.: ± 0.003 (+0.362...+0.367) - [0.0%] Duration: 34.3 seconds
3.	Rollout1	Bar/20* 4/1	eq: +0.347 (-0.032)
	Player: Opponent: 67.35% (G:0.81% B:0.02%) 32.65% (G:2.45% B:0.03%) Conf.: ± 0.002 (+0.345...+0.349) - [0.0%] Duration: 41.7 seconds
4.	Rollout1	Bar/20* 11/8	eq: +0.345 (-0.033)
	Player: Opponent: 67.27% (G:0.75% B:0.02%) 32.73% (G:0.58% B:0.00%) Conf.: ± 0.002 (+0.343...+0.348) - [0.0%] Duration: 29.2 seconds
5.	3-ply	Bar/20* 6/3	eq: +0.289 (-0.090)
	Player: Opponent: 64.43% (G:1.06% B:0.03%) 35.57% (G:2.17% B:0.02%)
1 1296 Games rolled with Variance Reduction. Moves and cube decisions: XG Roller

eXtreme Gammon Version: 2.10, MET: Rockwell-Kazaross

Best play for both b/20* 8/5.

Why best for regular backgammon: If you know opponent will not roll a 5 you have 25/36 chance of getting the closeout. On other rolls you could consider picking up the blot as the race would then be more favorable to you. If opponent rolls a 5 you rather would have not slotted but you would have been in an unfavorable position anyways. There is a 25/11 ratio of dancing rolls to non-dancing rolls. Rollout agrees with slotting play saying wins .7% more than next best play.

Why best for antigammon: If opponent enters with a 5 you want to be hit to take away your racing chances. That hit might happen with a later 5 as well.

2)

		White is Player 2 score: 0 pip: 37 1 point match pip: 14 score: 0 Blue is Player 1
XGID=-a--B-A-----a-------------:0:0:1:53:0:0:0:1:10
Blue to play 53

1.	3-ply	6/1* 4/1	eq: +0.670
	Player: Opponent: 83.48% (G:0.00% B:0.00%) 16.52% (G:0.00% B:0.00%)
2.	2-ply	6/3 4/Off	eq: +0.394 (-0.276)
	Player: Opponent: 69.69% (G:0.00% B:0.00%) 30.31% (G:0.00% B:0.00%)

eXtreme Gammon Version: 2.10, MET: Rockwell-Kazaross

Best play for both is 6/1* 4/1.

Why best for regular: Have a huge racing lead so minimizing shots is by far the most important thing. The alternative of 6/3 4/0 is a huge error.

Why best for anti: Have a huge racing lead so making him have to hit you has a high priority. 6/1* 4/1 forces him to do so with 44. The alternative of 6/3 4/0 means he has no rolls at all where he is forced to hit and usually just runs past (only rolls where me must stay giving a chance for a later hits are 22,33,23, 12). Additionally you get a better chance of winning from opponent getting big doubles twice since you are more likely to require a second roll to bearoff.

Messages In This Thread

• Antigammon puzzle
  Bob Koca -- Sunday, 30 June 2024, at 11:58 p.m.
  • Antigammon puzzle SOLUTION
    Bob Koca -- Tuesday, 2 July 2024, at 3:06 p.m.
    • Antigammon puzzle SOLUTION
      Timothy Chow -- Tuesday, 2 July 2024, at 4:58 p.m.
      • Antigammon puzzle SOLUTION
        Bob Koca -- Tuesday, 2 July 2024, at 8:27 p.m.