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Re: [Bug-gnubg] Cube eval going crazy on this one


From: Christian Anthon
Subject: Re: [Bug-gnubg] Cube eval going crazy on this one
Date: Tue, 10 Mar 2009 14:15:21 +0100

I haven't looked at the thread, but the net is rather bad in handling
late hits. Call it odd/even ply if you like, but it is just something
the net needs to be trained in, or a suitable sub-net should be
constructed. Anyway doing a cubeless rollout is better when the net is
bad, as the play is at least more reasonable, and you don't get the
win/loss fractions messed up by truncation using a bad net.

Christian.

On Thu, Feb 26, 2009 at 10:23 AM, Massimiliano Maini
<address@hidden> wrote:
>
> Hi all,
>
> on bgonline this cube decision has been posted and the evals returned by
> gnubg
> are crazy on even ply:
>
>     GNU Backgammon  Position ID: XgAAILftgAARAA
>                     Match ID   : AQEAAAAAAAAA
>     +-1--2--3--4--5--6-------7--8--9-10-11-12-+  O: gnubg (Cube: 2)
>     |    O  O  O  O  O |   |                  |  0 points
>     |    O  O  O  O  O |   |                  |  On roll
>     |    O           O |   |                  |
>     |                  |   |                  |
>     |                  |   |                  |
>     |                  |BAR|                  |^
>   X |                  |   |                  |
>  XX |    X             |   |                  |
>  XX |    X             |   |                  |
>  XX |    X             |   |                  |
>  XX | O  X  X  O       | X |                O |  0 points
>     +24-23-22-21-20-19------18-17-16-15-14-13-+  X: MaX
>
> The original one was in ma match, with score 9aw-9aw: I changed it to money
> to simplify since it doesn't make any difference.
>
> Cube analysis
> 0-ply cubeless equity  +0.190
>   0.610 0.000 0.000 - 0.390 0.027 0.003
> Cubeful equities:
> 1. No double            +0.398
> 2. Double, pass         +1.000  ( +0.602)
> 3. Double, take         +0.116  ( -0.282)
> Proper cube action: No redouble, take (31.9%)
>
> Cube analysis
> 1-ply cubeless equity  +0.464
>   0.747 0.000 0.000 - 0.253 0.027 0.003
> Cubeful equities:
> 1. Double, take         +0.756
> 2. Double, pass         +1.000  ( +0.244)
> 3. No double            +0.695  ( -0.062)
> Proper cube action: Redouble, take
>
> Cube analysis
> 2-ply cubeless equity  +0.245
>   0.637 0.000 0.000 - 0.363 0.026 0.003
> Cubeful equities:
> 1. No double            +0.462
> 2. Double, pass         +1.000  ( +0.538)
> 3. Double, take         +0.244  ( -0.218)
> Proper cube action: No redouble, take (28.9%)
>
> Cube analysis
> 3-ply cubeless equity  +0.503
>   0.765 0.000 0.000 - 0.235 0.025 0.003
> Cubeful equities:
> 1. Double, take         +0.844
> 2. Double, pass         +1.000  ( +0.156)
> 3. No double            +0.796  ( -0.048)
> Proper cube action: Redouble, take
>
> Cube analysis
> 4-ply cubeless equity  +0.288
>   0.658 0.000 0.000 - 0.342 0.025 0.003
> Cubeful equities:
> 1. No double            +0.532
> 2. Double, pass         +1.000  ( +0.468)
> 3. Double, take         +0.342  ( -0.189)
> Proper cube action: No redouble, take (28.8%)
>
> Position ID:        XgAAILftgAARAA
> Match ID:        AQEAAAAAAAAA
> Evaluator:         Crashed
>         Win     W(g)    W(bg)   L(g)    L(bg)   Equity    Cubeful
> static: 0.610   0.000   0.000   0.027   0.003    +0.190    +0.398
>  1 ply: 0.747   0.000   0.000   0.027   0.003    +0.464    +0.695
>  2 ply: 0.637   0.000   0.000   0.026   0.003    +0.245    +0.462
>  3 ply: 0.765   0.000   0.000   0.025   0.003    +0.503    +0.796
>  4 ply: 0.658   0.000   0.000   0.025   0.003    +0.288    +0.532
>
>
> Cubeless winning chances swing a lot between even and odd plies, while
> gammon and backgammon percentages are very stable.
> Notice that even W% increase 0/2/4ply, but so do odd ones 1ply/3ply.
>
> Can we still blame this on odd-even effect ?
>
> MaX.
>
> P.S.
> The thread on bgonline is this one:
>
> http://www.bgonline.org/forums/webbbs_config.pl?noframes;read=35362
>
> Neil said that it wasn't worth to do a 2ply cube rollout since the results
> would be garbage, due to the fact 2ply eval screws this position big time.
> However, the (stopped) rollout 2ply chequer/2ply cube gave the same result
> as the (stopped) rollout 2ply chequer/3ply cube and both were similar to
> 3ply
> eval. Rollout/eval figures are in this post:
>
> http://www.bgonline.org/forums/webbbs_config.pl?noframes;read=35416
>
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