[Bug-gnubg] Trivially simple position - but GNU can't handle it

[Neil Robins]

To my mind it should be very simple for a bot to come up with the right figures here and in similar positions. There is another bot out there that does not have these difficulties and gets exactly the same figures as the GNU rollout on its equivalent of GNU 2-ply and all higher plys.

 

Using the new MET I get.

 

 GNU Backgammon  Position ID: IQAA0AAAAAAAAA
                 Match ID   : UYnyAEAAAAAA
 +13-14-15-16-17-18------19-20-21-22-23-24-+     O: B
 |                  |   |    O           O | OOO 4 points
 |                  |   |                  | OOO
 |                  |   |                  | OOO
 |                  |   |                  | OO 
 |                  |   |                  | OO
v|                  |BAR|                  |     7 point match
 |                  |   |                  | XX
 |                  |   |                  | XX 
 |                  |   |                  | XX 
 |                  |   |          X       | XXX Rolled 54
 |                  |   |          X  X    | XXX 0 points
 +12-11-10--9--8--7-------6--5--4--3--2--1-+     X: A (Cube: 2)

 

Cube analysis
0-ply cubeless equity  -0.158 (Money:  -0.158)
  0.421 0.000 0.000 - 0.579 0.000 0.000
Cubeful equities:
1. Double, take         -0.093
2. Double, pass         +1.000  ( +1.093)
3. No double            -0.128  ( -0.035)
Proper cube action: Redouble, take

Cube analysis
1-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.118
2. Double, pass         +1.000  ( +1.118)
3. Double, take         -0.170  ( -0.053)
Proper cube action: No redouble, take (4.5%)

 

Cube analysis
2-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

Cube analysis
3-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

 

Cube analysis
4-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

 

Cube analysis
5-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

 

Cube analysis
6-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

 

Cube analysis
7-ply cubeless equity  -0.198 (Money:  -0.198)
  0.401 0.000 0.000 - 0.599 0.000 0.000
Cubeful equities:
1. No double            -0.137
2. Double, pass         +1.000  ( +1.137)
3. Double, take         -0.170  ( -0.034)
Proper cube action: No redouble, take (2.9%)

 

Rollout details:
Player A owns 2-cube:
  0.421 0.000 0.000 - 0.579 0.000 0.000 CL  -0.158 CF  -0.137
 [0.000 0.000 0.000 - 0.000 0.000 0.000 CL   0.000 CF   0.000]
Player B owns 4-cube:
  0.421 0.000 0.000 - 0.579 0.000 0.000 CL  -0.093 CF  -0.093
 [0.000 0.000 0.000 - 0.000 0.000 0.000 CL   0.000 CF   0.000]
Full cubeful rollout with var.redn.
129599 games, Mersenne Twister dice gen. with seed 849748376 and quasi-random dice
Play: world class 2-ply cubeful prune [world class]
keep the first 0 0-ply moves and up to 8 more moves within equity 0.16
Skip pruning for 1-ply moves.
Cube: 2-ply cubeful prune [world class]

 

BTW the rollout has stopped short of the set 129600 trials.

 

XGID=-A---A----------------ba--:1:-1:-1:00:4:0:0:7:10

Score is X:4 O:0 7 pt(s) match.
 +12-11-10--9--8--7-------6--5--4--3--2--1-+
 |                  |   |          O  O    | +---+
 |                  |   |          O       | | 2 |
 |                  |   |                  | +---+
 |                  |   |                  |
 |                  |   |                  |
 |                  |BAR|                  |
 |                  |   |                  |
 |                  |   |                  |
 |                  |   |                  |
 |                  |   |                  |
 |                  |   |    X           X |
 +13-14-15-16-17-18------19-20-21-22-23-24-+
Pipcount  X: 6  O: 8 X-O: 4-0/7
Cube  : 2, O own cube
O on roll, cube action

Analyzed in 3 ply
Player Winning Chances:    42.10% (G:  0.00% B:  0.00%)
Opponent Winning Chances:  57.90% (G:  0.00% B:  0.00%)

Cubeless Equities: No Redouble=-0.158, Redouble=-0.093

Cubeful Equities:
       No Redouble:   -0.137 (-0.044)
       Redouble/Take: -0.093
       Redouble/Drop: +1.000 (+1.093)

Best Cube action: Redouble / Take

eXtreme Gammon Version: 1.12, MET: Rockwell-Kazaross