1. Forum
  2. Usenet
  3. REC.GAMES.BACKGAMMON

  • That sound you hear? It's a board crunching

    From Timothy Chow@21:1/5 to All on Tue Sep 6 09:14:43 2022
    XGID=-CBBBbB--B-------b-bcBabc-:1:1:1:22:0:0:0:0:10

    X:Player 1 O:Player 2
    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O | | O O X O O O |
    | O | | O O X O O |
    | | | O O |
    | | | |
    | | | |
    | |BAR| |
    | | | |
    | | | |
    | | | X | +---+
    | X | | X O X X X X | | 2 |
    | X | | X O X X X X | +---+
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 93 O: 93 X-O: 0-0
    Cube: 2, X own cube
    X to play 22

    ---
    Tim Chow

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ah...Clem@21:1/5 to Timothy Chow on Tue Sep 6 11:45:57 2022
    On 9/6/2022 9:14 AM, Timothy Chow wrote:
    XGID=-CBBBbB--B-------b-bcBabc-:1:1:1:22:0:0:0:0:10

    X:Player 1   O:Player 2
    Score is X:0 O:0. Unlimited Game  +13-14-15-16-17-18------19-20-21-22-23-24-+
     |             O    |   | O  O  X  O  O  O |  |             O    |   | O  O  X     O  O |  |                  |   |    O           O |  |                  |   |                  |
     |                  |   |                  |
     |                  |BAR|                  |
     |                  |   |                  |
     |                  |   |                  |
     |                  |   |                X | +---+
     |          X       |   | X  O  X  X  X  X | | 2 |  |          X       |   | X  O  X  X  X  X | +---+  +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count  X: 93  O: 93 X-O: 0-0
    Cube: 2, X own cube
    X to play 22


    Race is even, so keeping the blocking point seems thematic. 6/2(2).

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Stick Rice@21:1/5 to ah...Clem on Tue Sep 6 10:46:07 2022
    On Tuesday, September 6, 2022 at 11:46:01 AM UTC-4, ah...Clem wrote:
    On 9/6/2022 9:14 AM, Timothy Chow wrote:
    XGID=-CBBBbB--B-------b-bcBabc-:1:1:1:22:0:0:0:0:10

    X:Player 1 O:Player 2
    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O | | O O X O O O |
    | O | | O O X O O |
    | | | O O |
    | | | |
    | | | |
    | |BAR| |
    | | | |
    | | | |
    | | | X | +---+
    | X | | X O X X X X | | 2 |
    | X | | X O X X X X | +---+
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 93 O: 93 X-O: 0-0
    Cube: 2, X own cube
    X to play 22

    Race is even, so keeping the blocking point seems thematic. 6/2(2).

    Right play maybe, wrong reasoning I'd guess.

    Stick

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From pepstein5@gmail.com@21:1/5 to Tim Chow on Thu Sep 8 02:16:18 2022
    On Tuesday, September 6, 2022 at 2:14:44 PM UTC+1, Tim Chow wrote:
    XGID=-CBBBbB--B-------b-bcBabc-:1:1:1:22:0:0:0:0:10

    X:Player 1 O:Player 2
    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O | | O O X O O O |
    | O | | O O X O O |
    | | | O O |
    | | | |
    | | | |
    | |BAR| |
    | | | |
    | | | |
    | | | X | +---+
    | X | | X O X X X X | | 2 |
    | X | | X O X X X X | +---+
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 93 O: 93 X-O: 0-0
    Cube: 2, X own cube
    X to play 22

    ---
    Tim Chow
    I can't recall Stick ever being wrong so 6/2(2) must be right.
    I'm also not at all sure that I would have played this.

    But I think I know the main reasons that this is correct.
    Let's look at the other candidates: 4/2(2) 3/1(2) is just too ugly.
    Hopefully, I wouldn't have played this even if I didn't have the solution in front of me.
    A strong board is likely to become useful and we have no reason to destroy it. Plays with 9/7(2) work badly if the opponent's next roll has no aces or twos. So 4/9 of the time, the opponent brings their rear checkers into the outfield, making our own
    escape difficult. I don't think I would have been terribly surprised if this play was right, though.
    It is correct that the blocking point is useful.
    One deficit of the correct play is that it wastes 4 pips which is expensive in an even race.
    So "the race is close" could also be an argument against the correct play -- maybe that's what
    Stick meant with his wrong-reason zinger.

    Paul

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Timothy Chow@21:1/5 to All on Thu Sep 8 08:47:06 2022
    XGID=-CBBBbB--B-------b-bcBabc-:1:1:1:22:0:0:0:0:10

    X:Player 1 O:Player 2
    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O | | O O X O O O |
    | O | | O O X O O |
    | | | O O |
    | | | |
    | | | |
    | |BAR| |
    | | | |
    | | | |
    | | | X | +---+
    | X | | X O X X X X | | 2 |
    | X | | X O X X X X | +---+
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 93 O: 93 X-O: 0-0
    Cube: 2, X own cube
    X to play 22

    Keeping the 9pt with 6/2(2) is double-edged. It will give X better
    chances of getting and hitting a shot, because it will be hard for O
    to jump both of her back checkers over X's 9pt. At the same time,
    it risks giving O better chances of getting and hitting a shot,
    because the 9pt is hard to clear safely.

    According to the rollout below, 6/4(2) is better. The fact that O's
    board has already started to crumble plays a role; see the variant.
    If X gets hit then he may have a chance to hit back from the bar, or
    at least will have an easier time entering against a four-point board
    than a five-point board.

    1. Rollout¹ 6/2(2) eq:-0.069
    Player: 41.73% (G:5.17% B:0.08%)
    Opponent: 58.27% (G:10.43% B:0.37%)
    Confidence: ±0.006 (-0.075..-0.063) - [100.0%]

    2. Rollout¹ 9/7(2) 6/4(2) eq:-0.124 (-0.055)
    Player: 39.40% (G:3.67% B:0.05%)
    Opponent: 60.60% (G:7.99% B:0.24%)
    Confidence: ±0.006 (-0.130..-0.118) - [0.0%]

    3. Rollout¹ 9/7(2) 4/2(2) eq:-0.155 (-0.086)
    Player: 38.10% (G:3.09% B:0.04%)
    Opponent: 61.90% (G:8.18% B:0.28%)
    Confidence: ±0.006 (-0.161..-0.149) - [0.0%]

    4. Rollout¹ 9/7(2) 3/1(2) eq:-0.155 (-0.086)
    Player: 38.05% (G:2.84% B:0.04%)
    Opponent: 61.95% (G:7.75% B:0.25%)
    Confidence: ±0.006 (-0.161..-0.150) - [0.0%]

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

    eXtreme Gammon Version: 2.19.207.pre-release

    -------
    Variant
    -------

    XGID=-CBBBbB--B-------b-bcBbbb-:1:1:1:22:0:0:0:0:10

    X:Player 1 O:Player 2
    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O | | O O X O O O |
    | O | | O O X O O O |
    | | | O |
    | | | |
    | | | |
    | |BAR| |
    | | | |
    | | | |
    | | | X | +---+
    | X | | X O X X X X | | 2 |
    | X | | X O X X X X | +---+
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 93 O: 95 X-O: 0-0
    Cube: 2, X own cube
    X to play 22

    1. Rollout¹ 9/7(2) 6/4(2) eq:-0.238
    Player: 35.49% (G:2.58% B:0.03%)
    Opponent: 64.51% (G:9.90% B:0.37%)
    Confidence: ±0.006 (-0.244..-0.232) - [100.0%]

    2. Rollout¹ 6/2(2) eq:-0.253 (-0.015)
    Player: 35.71% (G:3.39% B:0.04%)
    Opponent: 64.29% (G:12.32% B:0.39%)
    Confidence: ±0.006 (-0.259..-0.247) - [0.0%]

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

    eXtreme Gammon Version: 2.19.207.pre-release

    ---
    Tim Chow

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