[Bug-gnubg] Bug in analysis - position enclosed

[Ned Cross]

GNU build: 021022

OS: Win ME

Bug:  Analysis discontinuity

 

GNU exhibits strange behavior in this post-ace-point game position. 

 

1) GNU rates my move (completing the closeout) as a -.138 "bad move", giving an evaluation of 73.0% wins.

 

2) THEN, GNU rates the resulting position, in the next move pane, as a proper double/pass with an evaluation of 82.8% wins.

 

As a very colorful character I once knew would say:  "How can this be?!!"

 

Ned

 

__________________________

 

Move number 36: X to play 54

 

 GNU Backgammon  Position ID: bhsAALHtDkQAAQ
                 Match ID   : cInyABAAIAAA
 +13-14-15-16-17-18------19-20-21-22-23-24-+     O: GNUfish
 |       X          |   |    O  O  O  O  X | O   1 point
 |                  |   |    O  O  O  O    | O  
 |                  |   |             O    | O  
 |                  |   |                  | O  
 |                  |   |                  | O 
v|                  |BAR|                  |     7 point match (Cube: 1)
 |                  |   |                  |   
 |                  |   |                  |    
 |                  |   | X  X             |    
 |                  |   | X  X  X  X  X    |     Rolled 54
 | X                |   | X  X  X  X  X  O |     4 points
 +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: Ned

 

* Ned moves 6/1* 5/1

 

Cube analysis
2-ply cubeless equity  +0.293 (Money:  +0.289)
  0.679 0.000 0.000 - 0.321 0.067 0.002
1. No double            +0.440
2. Double, pass         +1.000  ( +0.560)
3. Double, take         +0.275  ( -0.165)
Proper cube action: No double, take (22.8%)
Alert: bad move ( -0.138)

 

Rolled 54 (+0.214):
     1. Cubeful 2-ply    24/19 5/1*                   Eq.:  +0.827
       0.774 0.000 0.000 - 0.226 0.067 0.004
*    2. Cubeful 2-ply    6/1* 5/1                     Eq.:  +0.689 ( -0.138)
       0.730 0.000 0.000 - 0.270 0.012 0.000
     3. Cubeful 1-ply    24/15                        Eq.:  +0.341 ( -0.486)
       0.621 0.000 0.000 - 0.379 0.043 0.001
     4. Cubeful 0-ply    24/19 12/8                   Eq.:  +0.359 ( -0.468)
       0.672 0.000 0.000 - 0.328 0.083 0.002
     5. Cubeful 0-ply    24/19 15/11                  Eq.:  +0.352 ( -0.475)
       0.671 0.000 0.000 - 0.329 0.086 0.002
     6. Cubeful 0-ply    12/7 5/1*                    Eq.:  +0.309 ( -0.518)
       0.666 0.000 0.000 - 0.334 0.096 0.007

 

Move number 37: X doubles to 2

 

 GNU Backgammon  Position ID: bhsAANq2DUQAAQ
                 Match ID   : cBHgABAAIAAA
 +13-14-15-16-17-18------19-20-21-22-23-24-+     O: GNUfish
 |       X          | O |    O  O  O  O  X | O   1 point
 |                  |   |    O  O  O  O    | O   Cube offered at 2
 |                  |   |             O    | O  
 |                  |   |                  | O  
 |                  |   |                  | O 
v|                  |BAR|                  |    
 |                  |   |                  |   
 |                  |   |                  |    
 |                  |   |                  |    
 |                  |   | X  X  X  X  X  X |    
 | X                |   | X  X  X  X  X  X |     4 points
 +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: Ned

 

* GNUfish rejects

 

Cube analysis
2-ply cubeless equity  +0.653 (Money:  +0.653)
  0.828 0.000 0.000 - 0.172 0.003 0.000
1. Double, pass         +1.000
2. Double, take         +1.255  ( +0.255)
3. No double            +0.931  ( -0.069)
Proper cube action: Double, pass
Ned wins 1 point