[Bug-gnubg] Eval

[Albert Silver]

There's something wrong with GNU's eval. Take the following position and
look at the respective evaluations at 0, 1, 2, and 3 plies.

GNU Backgammon  Position ID: vHsXAADCNhQCNw
                 Match ID   : MAEAAAAAAAAA
 +12-11-10--9--8--7-------6--5--4--3--2--1-+     O: White
 | O           O  O |   | O           O    |     0 points
 |             O  O |   | O                |     On roll
 |                  |   |                  |     
 |                  |   |                  |     
 |                  |   |                  |    
^|                  |BAR|                  |     (Cube: 1)
 |                  |   |                  |    
 |                  |   |    X     X       |     
 |                  |   | X  X  X  X  O    |     
 |                  |   | X  X  X  X  O  O |     
 | O           O  X |   | X  X  X  X  O  O |     0 points
 +13-14-15-16-17-18------19-20-21-22-23-24-+     X: Blue
Pip counts: O 203, X 69


Cube analysis
0-ply cubeless equity  -0.835
   34.8%   0.4%   0.0% -  65.2%  42.2%  11.5%
1. No double            -1.000
2. Double, pass         +1.000  ( +2.000)
3. Double, take         -2.080  ( -1.080)
Proper cube action: No double, take (35.1%)

Cube analysis
1-ply cubeless equity  -0.478
   45.5%   1.0%   0.0% -  54.5%  29.5%  10.2%
1. No double            -0.656
2. Double, pass         +1.000  ( +1.656)
3. Double, take         -1.390  ( -0.734)
Proper cube action: No double, beaver (30.7%)

Cube analysis
2-ply cubeless equity  -1.057
   29.5%   0.6%   0.0% -  70.5%  47.7%  17.6%
1. No double            -1.000
2. Double, pass         +1.000  ( +2.000)
3. Double, take         -2.487  ( -1.487)
Proper cube action: No double, take (42.7%)

Cube analysis
3-ply cubeless equity  -0.462
   46.8%   0.8%   0.0% -  53.2%  30.3%  10.4%
1. No double            -0.622
2. Double, pass         +1.000  ( +1.622)
3. Double, take         -1.349  ( -0.727)
Proper cube action: No double, beaver (30.9%)