I'm hoping some of the opening experts will comment on this one since I only partially understand the rollout results. First let me give the rollouts and then I'll give my thoughts.
          
 
         
 | | White is Player 2
score: 0
pip: 147 | Money session
Jacoby | pip: 160
score: 0
Blue is Player 1 |
|
| XGID=-a----E-CB-adC---badb---AA:0:0:1:31:0:0:1:0:10 |
| Blue to play 31 |
| 1. | Rollout1 | Bar/22 6/5 | eq: -0.509 |
| Player:
Opponent: | 37.43% (G:8.81% B:0.38%)
62.57% (G:23.39% B:1.18%) | Conf: ± 0.030 (-0.539...-0.479)
Duration: 3 hours 01 minute |
|
| 2. | Rollout1 | Bar/21 | eq: -0.578 (-0.069) |
| Player:
Opponent: | 36.81% (G:8.36% B:0.35%)
63.19% (G:20.47% B:0.91%) | Conf: ± 0.020 (-0.598...-0.558)
Duration: 2 hours 11 minutes |
|
| 3. | Rollout1 | Bar/22 24/23 | eq: -0.606 (-0.097) |
| Player:
Opponent: | 36.41% (G:8.34% B:0.38%)
63.59% (G:21.70% B:0.87%) | Conf: ± 0.023 (-0.629...-0.583)
Duration: 2 hours 14 minutes |
|
| |
1 1296 Games rolled with Variance Reduction.
Moves and cube decisions: 3 ply
|
eXtreme Gammon Version: 1.21
| | White is Player 2
score: 0
pip: 150 | Money session
Jacoby | pip: 160
score: 0
Blue is Player 1 |
|
| XGID=-a----E-CB-adC-a-b-db---AA:0:0:1:31:0:0:1:0:10 |
| Blue to play 31 |
| 1. | Rollout1 | Bar/22 24/23 | eq: -0.479 |
| Player:
Opponent: | 38.64% (G:8.88% B:0.38%)
61.36% (G:17.77% B:0.70%) | Conf: ± 0.014 (-0.493...-0.465)
Duration: 4 hours 58 minutes |
|
| 2. | Rollout1 | Bar/21 | eq: -0.540 (-0.060) |
| Player:
Opponent: | 37.85% (G:8.76% B:0.40%)
62.15% (G:20.00% B:0.88%) | Conf: ± 0.015 (-0.555...-0.525)
Duration: 4 hours 57 minutes |
|
| 3. | Rollout1 | Bar/22 6/5 | eq: -0.544 (-0.065) |
| Player:
Opponent: | 38.00% (G:9.24% B:0.48%)
62.00% (G:21.39% B:1.18%) | Conf: ± 0.018 (-0.562...-0.526)
Duration: 5 hours 33 minutes |
|
| |
1 2592 Games rolled with Variance Reduction.
Moves and cube decisions: 3 ply
|
eXtreme Gammon Version: 1.21
| | White is Player 2
score: 0
pip: 151 | Money session
Jacoby | pip: 160
score: 0
Blue is Player 1 |
|
| XGID=-a----E-CB-adCa--b-db---AA:0:0:1:31:0:0:1:0:10 |
| Blue to play 31 |
| 1. | Rollout1 | Bar/21 | eq: -0.457 |
| Player:
Opponent: | 39.29% (G:8.79% B:0.40%)
60.71% (G:17.57% B:0.73%) | Conf: ± 0.020 (-0.477...-0.437)
Duration: 2 hours 37 minutes |
|
| 2. | Rollout1 | Bar/22 24/23 | eq: -0.511 (-0.055) |
| Player:
Opponent: | 38.18% (G:8.77% B:0.39%)
61.82% (G:17.44% B:0.72%) | Conf: ± 0.020 (-0.531...-0.491)
Duration: 2 hours 21 minutes |
|
| 3. | Rollout1 | Bar/22 6/5 | eq: -0.512 (-0.055) |
| Player:
Opponent: | 38.31% (G:9.29% B:0.49%)
61.69% (G:20.48% B:1.02%) | Conf: ± 0.025 (-0.537...-0.487)
Duration: 2 hours 48 minutes |
|
| |
1 1296 Games rolled with Variance Reduction.
Moves and cube decisions: 3 ply
|
eXtreme Gammon Version: 1.21
Probably these should be rolled out 5184 times at least, but I have a slow computer and it seems unlikely to me that the top play will change, even if the sizes of the equity differences change somewhat.
Prior to seeing these results, I would have reasoned as follows. The opponent is developing a prime so I want to counter that strategy by trying for an advanced anchor and/or counterpriming. Though some amount of caution is indicated because we're slightly outboarded, we are behind in the race with more checkers back, and the opponent's position is more "primy" than "stacky" so we can afford some degree of boldness. In particular, bar/24 13/10 is unnecessarily cautious in all three cases. We should enter with a 3 and then decide whether the ace is 22/21, 24/23, or 6/5.
Although 6/5 unstacks the 6pt and starts a counterprime, I would have judged it to be slightly too bold in all three cases since the opponent already has the 5pt made. I don't like to slot while split unless I'm sure I know what I'm doing.
Slotting the more advanced anchor is the natural play, but the configuration of 2 checkers on the 5pt, 4 checkers on the 6pt, and 2 checkers on the 8pt often points to 24/23 because it aims a second checker at the 8pt, giving more return shots if the opponent uses one of those checkers for PoH. In particular I would have played 24/23 in the second position because 22/21 puts the more advanced checker under the gun of three builders. In the other two positions I would have played 22/21.
Thus I would have scored 2 out of 3, according to the rollout results. I still don't really understand why 6/5 seems to be so clear in the first position but so weak in the other two positions. Maybe it's because Blue's plight is more desperate in the first position and therefore Blue needs to take more drastic measures to try to equalize?
Incidentally, you might wonder why I didn't include a fourth variant, with White's blot on White's 9pt. That position was in fact the position I encountered OTB. I played bar/22 24/23, which a 1296-game GNU rollout didn't like, putting it 0.043 behind bar/21; however, a 1296-game XG rollout says that bar/21 and bar/22 24/23 are TCTC. (I could post these if someone wants.) Trying to understand the tradeoffs among the three different aces led me to consider the above three positions, which I think may be more instructive since it seems that a different play is best in each case.