[Bug-gnubg] Holding games

[Albert Silver]

The following position from Depreli's series came up in which GNU 0.14
chose one of the weakest replies:

GNU (O, 0 pts) vs. Albert (X, 0 pts) (money game)
Move number 6: O to play 63

    GNU Backgammon  Position ID: Ms/gBwBYd4PBAA
                    Match ID   : MAEPAAAAAAAA
    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  O: GNU
    |          O  O  O |   | O  O           X |  0 points
    |          O     O |   | O  O           X |  Rolled 63
    |                O |   | O              X |  
    |                  |   |                X |  
    |                  |   |                6 |  
    |                  |BAR|                  |^ (Cube: 1)
    |                  |   |                  |  
    |                X |   |                  |  
    |                X |   |                  |  
    |          X     X |   | O  X           O |  
    |    X     X     X |   | O  X           O |  0 points
    +24-23-22-21-20-19------18-17-16-15-14-13-+  X: Albert
Pip counts: O 130, X 128

* GNU moves 13/10 13/7

Rolled 63 (+0.019):
*1. Cubeful 2-ply    13/10 13/7           Eq.:  +0.214
    56.7%   2.3%   0.0% -  43.3%   0.7%   0.0%
 2. Cubeful 2-ply    8/5 8/2              Eq.:  +0.203 ( -0.012)
    56.1%   3.2%   0.0% -  43.9%   1.0%   0.0%
 3. Cubeful 2-ply    8/5 7/1              Eq.:  +0.202 ( -0.012)
    56.1%   3.1%   0.0% -  43.9%   1.0%   0.0%
 4. Cubeful 2-ply    8/2 7/4              Eq.:  +0.189 ( -0.025)
    55.8%   2.9%   0.0% -  44.2%   1.0%   0.0%
 5. Cubeful 2-ply    8/2 6/3              Eq.:  +0.188 ( -0.026)
    55.7%   3.0%   0.0% -  44.3%   1.0%   0.0%

MOVE            8/2 8/5         8/2 7/4         8/2 5/2         8/5 7/1
13/7 13/10 
BOTS' CHOICE S3, G13      G12                             S4
G14, J 
ROLLOUTS         0.098   0.084   0.077   0.074   0.058
Rollouts by SW3.2 1296 trials 2ply huge 3ply cube with bearoff database.

BTW, G12 is Gnu 0.12, G13, Gnu 0.13 etc.


Neil Kazaross, who had chosen the correct move unsurprisingly, added:
We see an example of why I am hoping more training in holding games will
improve GNU even more.


                                                        Albert