• Just another priming battle

    From Timothy Chow@21:1/5 to All on Fri Dec 29 08:53:10 2023
    XGID=-a---BCBC----C-babccc---AA:0:0:1:33:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | X O O O O | | O O X |
    | X O O O | | O O |
    | X O | | O O |
    | | | |
    | | X | |
    | |BAR| |
    | | | |
    | | | |
    | X | | X |
    | X X | | X X |
    | X X | | X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 154 O: 123 X-O: 0-0
    Cube: 1
    X to play 33

    ---
    Tim Chow

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Timothy Chow@21:1/5 to All on Sun Dec 31 09:26:44 2023
    XGID=-a---BCBC----C-babccc---AA:0:0:1:33:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | X O O O O | | O O X |
    | X O O O | | O O |
    | X O | | O O |
    | | | |
    | | X | |
    | |BAR| |
    | | | |
    | | | |
    | X | | X |
    | X X | | X X |
    | X X | | X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 154 O: 123 X-O: 0-0
    Cube: 1
    X to play 33

    Stepping up both checkers to the edge of a prime even when there is a significant risk of being pointed on is a common theme. But I often see
    players eschewing it, reasoning that there's no point in stepping up if
    we're just going to get pointed on. That kind of logic is often valid
    if the opponent has a blitzing threat, but this is a priming position.
    For example, suppose we step up with 24/21 and O rolls a 4. She is then
    faced with a choice of pointing on her 4pt or her 3pt. Pointing on her
    4pt comes at the cost of giving up her 8pt and giving X a considerable
    number of return shots. Pointing on her 3pt is safer, but allows X to
    anchor with a 4 and to hit back with some 5's. By contrast, if X stays
    back and plays something like bar/22 13/10(2) 8/5, then O's 4's play
    much better.

    With a spare on O's 8pt (Variant 1) the rollout says that the decision
    is much closer. Also see Variant 2, where X has the option of making
    his 3pt.

    1. Rollout¹ Bar/22 24/21 13/10(2) eq:-0.424
    Player: 43.29% (G:8.40% B:0.44%)
    Opponent: 56.71% (G:28.29% B:1.05%)
    Confidence: ±0.012 (-0.436..-0.412) - [100.0%]

    2. Rollout¹ Bar/22 13/10(2) 8/5 eq:-0.501 (-0.076)
    Player: 40.33% (G:8.73% B:0.39%)
    Opponent: 59.67% (G:24.37% B:1.16%)
    Confidence: ±0.015 (-0.516..-0.485) - [0.0%]

    3. Rollout¹ Bar/22 13/10(3) eq:-0.517 (-0.093)
    Player: 40.14% (G:8.18% B:0.38%)
    Opponent: 59.86% (G:24.13% B:1.01%)
    Confidence: ±0.016 (-0.533..-0.501) - [0.0%]

    ¹ 1296 Games rolled with Variance Reduction.
    Dice Seed: 271828
    Moves: 3-ply, cube decisions: XG Roller

    eXtreme Gammon Version: 2.19.211.pre-release

    ---------
    Variant 1
    ---------

    XGID=-a---BCBC----C-bacccb---AA:0:0:1:33:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | X O O O O | | O O X |
    | X O O O | | O O |
    | X O O | | O |
    | | | |
    | | X | |
    | |BAR| |
    | | | |
    | | | |
    | X | | X |
    | X X | | X X |
    | X X | | X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 154 O: 126 X-O: 0-0
    Cube: 1
    X to play 33

    1. Rollout¹ Bar/22 24/21 13/10(2) eq:-0.443
    Player: 42.41% (G:8.86% B:0.45%)
    Opponent: 57.59% (G:26.95% B:1.10%)
    Confidence: ±0.010 (-0.453..-0.434) - [91.0%]

    2. Rollout¹ Bar/22 13/10(2) 8/5 eq:-0.454 (-0.011)
    Player: 40.53% (G:9.26% B:0.39%)
    Opponent: 59.47% (G:21.85% B:1.07%)
    Confidence: ±0.012 (-0.467..-0.442) - [9.0%]

    3. Rollout² Bar/22 13/10(3) eq:-0.477 (-0.034)
    Player: 40.01% (G:8.57% B:0.41%)
    Opponent: 59.99% (G:21.03% B:0.87%)
    Confidence: ±0.016 (-0.493..-0.461) - [0.0%]

    ¹ 2592 Games rolled with Variance Reduction.
    Dice Seed: 271828
    Moves: 3-ply, cube decisions: XG Roller

    ² 1296 Games rolled with Variance Reduction.
    Dice Seed: 271828
    Moves: 3-ply, cube decisions: XG Roller

    eXtreme Gammon Version: 2.19.211.pre-release

    ---------
    Variant 2
    ---------

    XGID=-a---BCBCA---B-babccc---AA:0:0:1:33:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | X O O O O | | O O X |
    | X O O O | | O O |
    | O | | O O |
    | | | |
    | | X | |
    | |BAR| |
    | | | |
    | | | |
    | X | | X |
    | X X | | X X |
    | X X X | | X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 150 O: 123 X-O: 0-0
    Cube: 1
    X to play 33

    1. Rollout¹ Bar/22 9/3 6/3 eq:-0.445
    Player: 41.31% (G:9.00% B:0.45%)
    Opponent: 58.69% (G:23.40% B:1.13%)
    Confidence: ±0.011 (-0.456..-0.434) - [99.8%]

    2. Rollout¹ Bar/22 24/21 13/10(2) eq:-0.466 (-0.021)
    Player: 41.40% (G:8.44% B:0.42%)
    Opponent: 58.60% (G:29.17% B:1.36%)
    Confidence: ±0.009 (-0.475..-0.457) - [0.2%]

    ¹ 2592 Games rolled with Variance Reduction.
    Dice Seed: 271828
    Moves: 3-ply, cube decisions: XG Roller

    eXtreme Gammon Version: 2.19.211.pre-release

    ---
    Tim Chow

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)