[bug-gnubg] bug in gammon-save eval

[Ned Cross]

GNU is choosing a move that loses more gammons because it has a fantasy that there are actual game-winning chances from this position.  Very strange.

 

-Ned

 

 

black (O, 10 pts) vs. white (X, 1 pts) (Match to 15)

 

Game number 6

 

Match Information:

 

black's rating: n/a
white's rating: n/a
Date: n/a
Event: n/a
Round: n/a
Place: n/a
Annotator: n/a
Comments: n/a
Move number 47: X to play 34

 

 GNU Backgammon  Position ID: HQAAYLYbsgAAAA
                 Match ID   : UYnxAaAACAAA
 +13-14-15-16-17-18------19-20-21-22-23-24-+     O: black
 | X                |   |             O  O | OOO 10 points
 |                  |   |             O    | OO 
 |                  |   |             O    | OO 
 |                  |   |                  | OO 
 |                  |   |                  | OO
v|                  |BAR|                  |     15 point match
 |                  |   |                  |   
 |                  |   |                  |    
 |                  |   |    X             |    
 | X                |   | X  X  X  X     X |     Rolled 34
 | X     X          |   | X  X  X  X     X |     1 point
 +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: white (Cube: 2)
Pip counts: O 7, X 90

 

* white moves 13/6

 

Cube analysis
2-ply cubeless equity  -1.630 (Money:  -1.936)
  0.000 0.000 0.000 - 1.000 0.936 0.000
Cubeful equities:
  2-ply cubeful 100% speed [world class]
1. No double            -1.630
2. Double, pass         +1.000  ( +2.630)
3. Double, take         -1.894  ( -0.264)
Proper cube action: No redouble, take (9.1%)

 

Rolled 34 (-0.023):
     1. Cubeful 2-ply    13/10 12/8                   Eq.:  -1.629
       0.008 0.002 0.000 - 0.992 0.974 0.000
*    2. Cubeful 2-ply    13/6                         Eq.:  -1.647 ( -0.018)
       0.000 0.000 0.000 - 1.000 0.962 0.000
     3. Cubeful 2-ply    12/9 10/6                    Eq.:  -1.663 ( -0.034)
       0.000 0.000 0.000 - 1.000 0.986 0.000
     4. Cubeful 2-ply    13/9 12/9                    Eq.:  -1.663 ( -0.034)
       0.000 0.000 0.000 - 1.000 0.986 0.000
     5. Cubeful 2-ply    12/5                         Eq.:  -1.665 ( -0.036)
       0.000 0.000 0.000 - 1.000 0.988 0.000
     6. Cubeful 2-ply    13/9 10/7                    Eq.:  -1.667 ( -0.038)
       0.000 0.000 0.000 - 1.000 0.991 0.000

 

Output generated Fri Apr 25 13:38:59 2003
by GNU Backgammon 0.13-devel (Text Export version 1.38)