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Backgames: Can we trust XG version 2?

Posted By: Timothy Chow
Date: Monday, 11 July 2011, at 5:12 p.m.

I'm curious as to how much we can trust 3-ply rollouts of backgames in XG version 2. Stick gave some examples in this post of positions where we have every reason to be skeptical of XG 3-ply's choice. Below I give four positions from a game I played recently against XG version 1, where 3-ply disagrees noticeably from XGR+. (I've put the 3-ply and XGR+ evaluations of the same position side by side. This is my first attempt to follow Nack's instructions to post side-by-side diagrams, so I hope it comes out O.K.) When 3-ply plays this unreliably, even a 3-ply rollout is open to question.

I'm hoping that somebody who has XG version 2 can run these positions (and Stick's positions) through 3-ply evaluation and XGR+, to see whether XG version 2 looks significantly more trustworthy in this important but notoriously difficult part of the game. Any volunteers?







White is Timothy Chow

score: 4
pip: 82
7 point match
pip: 211
score: 3

Blue is eXtremeGammon
XGID=---ABAB-A---A---abbbccCbCA:1:1:1:61:3:4:0:7:10
Blue to play 61

1.3 plyBar/24 22/16* eq: +0.381
Player:
Opponent:		 47.13% (G:1.15% B:0.03%)
52.87% (G:42.43% B:15.33%)
2.3 plyBar/24 12/6eq: +0.329 (-0.053)
Player:
Opponent:		 46.04% (G:2.00% B:0.08%)
53.96% (G:36.53% B:9.94%)
3.3 plyBar/24 8/2eq: +0.230 (-0.152)
Player:
Opponent:		 44.00% (G:1.89% B:0.08%)
56.00% (G:39.30% B:11.00%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross





White is Timothy Chow

score: 4
pip: 82
7 point match
pip: 211
score: 3

Blue is eXtremeGammon
XGID=---ABAB-A---A---abbbccCbCA:1:1:1:61:3:4:0:7:10
Blue to play 61

1.XG Roller+Bar/24 12/6eq: +0.330
Player:
Opponent:		 46.07% (G:2.68% B:0.10%)
53.93% (G:36.89% B:9.30%)
2.XG Roller+Bar/24 8/2eq: +0.184 (-0.146)
Player:
Opponent:		 43.07% (G:1.99% B:0.08%)
56.93% (G:39.88% B:10.45%)
3.XG Roller+Bar/24 22/16* eq: +0.139 (-0.191)
Player:
Opponent:		 42.12% (G:2.04% B:0.10%)
57.88% (G:40.83% B:15.25%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross
White is Timothy Chow

score: 4
pip: 92
7 point match
pip: 224
score: 3

Blue is eXtremeGammon
XGID=---ABaB-A---A---AbbbbdBbDA:1:1:1:32:3:4:0:7:10
Blue to play 32

1.3 plyBar/22 16/14eq: +0.395
Player:
Opponent:		 47.41% (G:1.35% B:0.04%)
52.59% (G:38.90% B:13.08%)
2.3 plyBar/22 24/22eq: +0.371 (-0.024)
Player:
Opponent:		 46.92% (G:1.75% B:0.05%)
53.08% (G:37.87% B:11.68%)
3.3 plyBar/22 8/6eq: +0.370 (-0.024)
Player:
Opponent:		 46.91% (G:1.83% B:0.05%)
53.09% (G:38.41% B:11.07%)
4.3 plyBar/22 12/10eq: +0.351 (-0.044)
Player:
Opponent:		 46.51% (G:1.27% B:0.04%)
53.49% (G:38.87% B:12.92%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross





White is Timothy Chow

score: 4
pip: 92
7 point match
pip: 224
score: 3

Blue is eXtremeGammon
XGID=---ABaB-A---A---AbbbbdBbDA:1:1:1:32:3:4:0:7:10
Blue to play 32

1.XG Roller+Bar/22 8/6eq: +0.313
Player:
Opponent:		 45.72% (G:2.63% B:0.11%)
54.28% (G:37.79% B:11.51%)
2.XG Roller+Bar/22 24/22eq: +0.207 (-0.106)
Player:
Opponent:		 43.53% (G:2.39% B:0.11%)
56.47% (G:38.94% B:12.40%)
3.XG Roller+Bar/22 12/10eq: +0.180 (-0.134)
Player:
Opponent:		 42.97% (G:2.12% B:0.09%)
57.03% (G:40.03% B:13.53%)
4.XG Roller+Bar/22 16/14eq: +0.175 (-0.138)
Player:
Opponent:		 42.88% (G:2.28% B:0.09%)
57.12% (G:40.18% B:13.64%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross
White is Timothy Chow

score: 4
pip: 83
7 point match
pip: 230
score: 3

Blue is eXtremeGammon
XGID=---AB-B-A---A-a--bbbbdCbDA:1:1:-1:32:3:4:0:7:10
White to play 32

1.3 ply8/6 7/4eq: -0.027
Player:
Opponent:		 60.19% (G:42.55% B:14.49%)
39.81% (G:1.29% B:0.02%)
2.3 ply8/5 7/5eq: -0.055 (-0.028)
Player:
Opponent:		 59.61% (G:42.19% B:15.10%)
40.39% (G:1.27% B:0.02%)
3.3 ply7/5 7/4eq: -0.059 (-0.032)
Player:
Opponent:		 59.53% (G:42.43% B:14.95%)
40.47% (G:1.45% B:0.02%)
4.3 ply11/9 7/4eq: -0.087 (-0.060)
Player:
Opponent:		 58.95% (G:40.75% B:13.43%)
41.05% (G:2.01% B:0.03%)
5.3 ply8/6 8/5eq: -0.115 (-0.088)
Player:
Opponent:		 58.37% (G:40.76% B:14.10%)
41.63% (G:1.41% B:0.02%)
6.3 ply11/9 8/5eq: -0.122 (-0.096)
Player:
Opponent:		 58.21% (G:40.51% B:13.62%)
41.79% (G:1.84% B:0.03%)
7.3 ply11/6eq: -0.191 (-0.164)
Player:
Opponent:		 56.80% (G:39.17% B:12.90%)
43.20% (G:1.92% B:0.03%)
8.3 ply11/8 7/5eq: -0.197 (-0.171)
Player:
Opponent:		 56.67% (G:39.71% B:12.86%)
43.33% (G:1.77% B:0.03%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross





White is Timothy Chow

score: 4
pip: 83
7 point match
pip: 230
score: 3

Blue is eXtremeGammon
XGID=---AB-B-A---A-a--bbbbdCbDA:1:1:-1:32:3:4:0:7:10
White to play 32

1.XG Roller+7/5 7/4eq: -0.062
Player:
Opponent:		 59.50% (G:41.73% B:12.81%)
40.50% (G:1.05% B:0.02%)
2.XG Roller+8/5 7/5eq: -0.095 (-0.033)
Player:
Opponent:		 58.78% (G:41.64% B:13.38%)
41.22% (G:1.07% B:0.03%)
3.XG Roller+8/6 7/4eq: -0.101 (-0.038)
Player:
Opponent:		 58.69% (G:41.04% B:13.06%)
41.31% (G:1.01% B:0.02%)
4.XG Roller+11/9 7/4eq: -0.116 (-0.054)
Player:
Opponent:		 58.35% (G:40.76% B:12.08%)
41.65% (G:1.68% B:0.04%)
5.XG Roller+11/9 8/5eq: -0.144 (-0.082)
Player:
Opponent:		 57.77% (G:40.59% B:12.21%)
42.23% (G:1.88% B:0.05%)
6.XG Roller+8/6 8/5eq: -0.150 (-0.087)
Player:
Opponent:		 57.65% (G:40.40% B:12.13%)
42.35% (G:1.32% B:0.03%)
7.XG Roller+11/8 7/5eq: -0.152 (-0.090)
Player:
Opponent:		 57.60% (G:40.78% B:11.67%)
42.40% (G:1.45% B:0.04%)
8.XG Roller+11/6eq: -0.199 (-0.137)
Player:
Opponent:		 56.63% (G:39.64% B:11.15%)
43.37% (G:1.69% B:0.04%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross
White is Timothy Chow

score: 4
pip: 73
7 point match
pip: 226
score: 3

Blue is eXtremeGammon
XGID=---AB-BA----A-----ccbeDbD-:1:1:1:42:3:4:0:7:10
Blue to play 42

1.3 ply12/10 7/3eq: +0.314
Player:
Opponent:		 45.74% (G:1.76% B:0.08%)
54.26% (G:36.22% B:10.82%)
2.3 ply24/22 7/3eq: +0.288 (-0.026)
Player:
Opponent:		 45.21% (G:1.90% B:0.08%)
54.79% (G:35.78% B:10.25%)
3.3 ply12/8 7/5eq: +0.287 (-0.027)
Player:
Opponent:		 45.18% (G:1.41% B:0.07%)
54.82% (G:37.00% B:11.62%)
4.3 ply12/6eq: +0.266 (-0.048)
Player:
Opponent:		 44.75% (G:1.33% B:0.06%)
55.25% (G:37.15% B:11.65%)
5.3 ply24/22 12/8eq: +0.239 (-0.075)
Player:
Opponent:		 44.20% (G:1.54% B:0.07%)
55.80% (G:37.41% B:11.37%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross





White is Timothy Chow

score: 4
pip: 73
7 point match
pip: 226
score: 3

Blue is eXtremeGammon
XGID=---AB-BA----A-----ccbeDbD-:1:1:1:42:3:4:0:7:10
Blue to play 42

1.XG Roller+24/22 7/3eq: +0.425
Player:
Opponent:		 48.03% (G:2.56% B:0.08%)
51.97% (G:36.64% B:9.29%)
2.XG Roller+12/10 7/3eq: +0.388 (-0.037)
Player:
Opponent:		 47.27% (G:2.37% B:0.08%)
52.73% (G:37.08% B:9.78%)
3.XG Roller+12/8 7/5eq: +0.342 (-0.083)
Player:
Opponent:		 46.32% (G:2.10% B:0.07%)
53.68% (G:38.08% B:10.51%)
4.XG Roller+24/22 12/8eq: +0.320 (-0.105)
Player:
Opponent:		 45.86% (G:1.99% B:0.07%)
54.14% (G:38.29% B:10.07%)
5.XG Roller+12/6eq: +0.316 (-0.109)
Player:
Opponent:		 45.79% (G:1.87% B:0.06%)
54.21% (G:38.30% B:10.50%)

eXtreme Gammon Version: 1.21, MET: Rockwell-Kazaross

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