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  • 0-1 backgame

    From Timothy Chow@21:1/5 to All on Fri Dec 17 23:15:17 2021
    I sometimes joke that in positions like the one below, O is playing
    a "0-1 backgame."


    XGID=bcBBCCB-C--------b-bbbb---:1:-1:1:33:0:0:0:0:10

    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 O O | +---+
    | O | | O O O O | | 2 |
    | | | | +---+
    | | | |
    | | | |
    | |BAR| |
    | | O | |
    | | O | |
    | X | | X X O |
    | X | | X X X X X O |
    | X | | X X X X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 73 O: 174 X-O: 0-0
    Cube: 2, O own cube
    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 19 20:36:52 2021
    XGID=bcBBCCB-C--------b-bbbb---:1:-1:1:33:0:0:0:0:10

    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 O O | +---+
    | O | | O O O O | | 2 |
    | | | | +---+
    | | | |
    | | | |
    | |BAR| |
    | | O | |
    | | O | |
    | X | | X X O |
    | X | | X X X X X O |
    | X | | X X X X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 73 O: 174 X-O: 0-0
    Cube: 2, O own cube
    X to play 33

    Despite having seen this type of "pre-clearing" play numerous times
    before, I still tend to miss it OTB.

    1. Rollout¹ 8/5(2) 6/3(2) eq:+1.240
    Player: 79.12% (G:60.24% B:14.57%)
    Opponent: 20.88% (G:0.01% B:0.00%)
    Confidence: ±0.009 (+1.231..+1.249) - [100.0%]

    2. Rollout¹ 8/2 6/3(2) eq:+1.141 (-0.099)
    Player: 76.72% (G:58.53% B:13.18%)
    Opponent: 23.28% (G:0.27% B:0.01%)
    Confidence: ±0.010 (+1.131..+1.150) - [0.0%]

    3. Rollout¹ 8/5(2) 8/2 eq:+1.104 (-0.136)
    Player: 74.60% (G:57.01% B:15.60%)
    Opponent: 25.40% (G:0.00% B:0.00%)
    Confidence: ±0.010 (+1.094..+1.114) - [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)
  • From Timothy Chow@21:1/5 to All on Thu Sep 14 08:52:34 2023
    The subject line is a joke that my playing group enjoys.

    XGID=bcBCBCCB---------bccb-----:1:-1:1:44:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O O | | O O | +---+
    | O O | | O O | | 2 |
    | O | | O | +---+
    | | | |
    | | | |
    | |BAR| |
    | | O | |
    | | O | |
    | | | X X X O |
    | X | | X X X X X O |
    | X | | X X X X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 68 O: 187 X-O: 0-0
    Cube: 2, O own cube
    X to play 44

    ---
    Tim Chow

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From ah....Clem@21:1/5 to Timothy Chow on Thu Sep 14 13:06:15 2023
    On 9/14/2023 8:52 AM, Timothy Chow wrote:
    The subject line is a joke that my playing group enjoys.

    Many people claim that a 1-5 backgame structure is the weakest, but the
    0-1 structure seems to be worse.


    XGID=bcBCBCCB---------bccb-----:1:-1:1:44:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
     +13-14-15-16-17-18------19-20-21-22-23-24-+
     |             O  O |   | O  O             | +---+
     |             O  O |   | O  O             | | 2 |
     |                O |   | O                | +---+
     |                  |   |                  |
     |                  |   |                  |
     |                  |BAR|                  |
     |                  | O |                  |
     |                  | O |                  |
     |                  |   | X  X     X     O |
     |                X |   | X  X  X  X  X  O |
     |                X |   | X  X  X  X  X  O |
     +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count  X: 68  O: 187 X-O: 0-0
    Cube: 2, O own cube
    X to play 44


    If the race were closer and O stood more of a chance of running off the
    gammon I'd look seriously at taking two off now. But I don't think it's
    worth risking leaving a gap for a marginal increase (assuming it
    actually is an increase) in gammons.

    So, I'll clear the 6 and play 7/3. It exposes no shots and leaves X even
    ended. 7/3 6/2(3)


    --
    Ah....Clem
    The future is fun, the future is fair.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Timothy Chow@21:1/5 to All on Sat Sep 16 08:56:58 2023
    XGID=bcBCBCCB---------bccb-----:1:-1:1:44:0:0:0:0:10

    Score is X:0 O:0. Unlimited Game
    +13-14-15-16-17-18------19-20-21-22-23-24-+
    | O O | | O O | +---+
    | O O | | O O | | 2 |
    | O | | O | +---+
    | | | |
    | | | |
    | |BAR| |
    | | O | |
    | | O | |
    | | | X X X O |
    | X | | X X X X X O |
    | X | | X X X X X O |
    +12-11-10--9--8--7-------6--5--4--3--2--1-+
    Pip count X: 68 O: 187 X-O: 0-0
    Cube: 2, O own cube
    X to play 44

    O has enough checkers back that backgammons are relevant. The
    aggressive bearoff play of 7/3(2) 4/off(2) does win slightly more
    backgammons. However, as you might expect, that interior gap comes
    with a significantly higher risk of blotting later. Clearing the
    6pt with 7/3 6/2(3) does give O a 66 joker but is otherwise a safer
    play.

    Another thing to be aware of is that often, in the endgame, the
    more aggressive bearoff play wins more gammons. But here, X's
    lead in the pip count is so huge that winning a gammon is not a
    matter of winning the gammon race. As long as X is not hit, the
    gammon is pretty much in the bag. So the safer play will win
    more games *and* gammons. To justify a risk requires a *lot* of
    extra backgammon wins, which just aren't available here.

    1. Rollout¹ 7/3 6/2(3) eq:+1.124
    Player: 75.66% (G:60.55% B:12.10%)
    Opponent: 24.34% (G:0.26% B:0.01%)
    Confidence: ±0.010 (+1.113..+1.134) - [100.0%]

    2. Rollout¹ 7/3(2) 4/Off(2) eq:+0.995 (-0.129)
    Player: 71.39% (G:54.40% B:15.58%)
    Opponent: 28.61% (G:0.00% B:0.00%)
    Confidence: ±0.014 (+0.981..+1.009) - [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

    ---
    Tim Chow

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