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## Re: [Bug-gnubg] Huge evaluation difference

 From: Øystein Schønning-Johansen Subject: Re: [Bug-gnubg] Huge evaluation difference Date: Thu, 21 Mar 2019 12:54:45 +0100

Sure I can. The system actually calculates the probability of saving gammon for all possible position that can come up. (That's the dynamic programming part) So, since I've already calculated all these probabilities, it's easy to get those numbers after a specific roll+move.

#off:  0  board: 2----3|63----|1-----|-----
chk(bb): x----x|xx----|x-----|----- back: 13 #out: 10 #cross: 26
#off:  7  board: 2231--|------|------|-----
chk(bb): xxxx--|------|------|----- back:  4 #out:  0 #cross:  8
Cubeless prob. of saving gammon: 0.129424
16: 13/12 12/6  -> 0.913103
16: 13/12 8/2   -> 0.938736
16: 13/12 7/1   -> 0.942557
16: 8/7 8/2     -> 0.984595
16: 8/7 7/1     -> 0.984930
16: 7/6 7/1     -> 0.922614
61: 13/7 8/7    -> 0.984416
61: 13/7 6/5    -> 0.984048
61: 8/2 7/6     -> 0.915246
61: 8/2 6/5     -> 0.984322
61: 7/1 6/5     -> 0.984760

Note that I didn't bother to order the moves in the printout. That will be available in next version. :-)
And since this is with the other player on roll, it is then the probability of winning gammon for the other player that is listed. The best move is therefore the move with lowest value, 13/6, listed at the top..

-Øystein

On Wed, Mar 20, 2019 at 11:10 PM Philippe Michel <address@hidden> wrote:
On Wed, Mar 20, 2019 at 11:40:41AM +0100, ?ystein Sch?nning-Johansen wrote:

> I managed to calculate the gammon saving probability of the posted position
> in a few minutes using about 15GB of memory. (I also have a slower version
> of the tool that uses sparse matrices to store the probabilities, but I did
> not try that today)
>
> 2000036300001 2231
> #off:  0  board: 2----3|63----|1-----|-----
>         chk(bb): x----x|xx----|x-----|----- back: 13 #out: 10 #cross: 26
> #off:  7  board: 2231--|------|------|-----
>         chk(bb): xxxx--|------|------|----- back:  4 #out:  0 #cross:  8
> Cubeless prob. of saving gammon: 0.129424

This is not directly comparable with the numbers below since your number
is before the roll. Can you compute it from the other side (probability
of winning a gammon) for the first 2 or 3 choices of playing a 61 roll ?

> >     1. Cubeful 2-ply    13/6                         Eq.: -2.201
> >        0.000 0.000 0.000 - 1.000 0.913 0.000
> >         2-ply cubeful prune [world class]
> >     2. Cubeful 2-ply    8/2 7/6                      Eq.: -2.204 (-0.003)
> >        0.000 0.000 0.000 - 1.000 0.915 0.000
> >         2-ply cubeful prune [world class]
> >     3. Cubeful 2-ply    7/6 7/1                      Eq.: -2.213 (-0.013)
> >        0.000 0.000 0.000 - 1.000 0.923 0.000
> >         2-ply cubeful prune [world class]
> >     4. Cubeful 2-ply    13/12 8/2                    Eq.: -2.234 (-0.034)
> >        0.000 0.000 0.000 - 1.000 0.939 0.000
> >         2-ply cubeful prune [world class]
> >     5. Cubeful 2-ply    13/12 7/1                    Eq.: -2.240 (-0.039)
> >        0.000 0.000 0.000 - 1.000 0.943 0.000
> >         2-ply cubeful prune [world class]
> >     6. Cubeful 2-ply    13/7 6/5                     Eq.: -2.294 (-0.093)
> >        0.000 0.000 0.000 - 1.000 0.984 0.000
> >         2-ply cubeful prune [world class]