Cubeless rollout of a cube position

[Ian Shaw]

Does it make sense to do a cubeless rollout of a cube position? I see that if I ask for one, gnubg automatically ticks the Cubeful Rollout box and does a cubeful rollout.

 

But if the bot doesn’t understand the position, it may erroneously pass future cubes and give a bad result. For example, 9 out of these 36 games ended in Double/ Pass on the 2-cube rollout, and 14/36 on the 4-cube rollout. This is only a test; I know more than 36 games are required to draw any conclusions.

 

This is a position that Frank Berger has suggested, on DailyGammon, that the bot doesn’t understand. “XGID=------a----------BBCCBBAn-:1:1:1:00:0:0:0:0:10 XG believes to be a 60-70% favorite for the straggler player depending on ply/rollout but the positions is only about 6%” . I wanted to see what Gnubg thinks.

 

The 2-ply evaluation suggest 40% wins; rollouts suggest 70%. But can I trust this if the cube actions are wrong? I would expect a cubeless rollout to help eliminate this bias so that games are played to a conclusion (leaving only chequer play errors)

 

 

/z8AAAEAANvdFg:UYkNAAAAAAAE

 

Note that the Copy window is reversing the players’ win-loss breakdown in the results below. The GUI has them the correct way.

 

Cube analysis

Rollout cubeless equity -0.1968

 

Cubeful equities:

1. No double           -0.6901

2. Double, pass        -1.0000  (-0.3099)

3. Double, take        -0.5094  (+0.1808)

Proper cube action: No redouble, take (36.8%)

 

Rollout details:

ianshaw owns 2-cube:

  0.2934 0.2533 0.0028 - 0.7066 0.0398 0.0000 CL -0.1967 CF -0.6901

[0.0418 0.0370 0.0019 - 0.0418 0.0144 0.0002 CL  0.1242 CF  0.1798]

gnubg owns 4-cube:

  0.2856 0.2425 0.0010 - 0.7144 0.0000 0.0001 CL -0.3652 CF -0.5094

[0.0442 0.0414 0.0011 - 0.0442 0.0235 0.0005 CL  0.2649 CF  0.3471]

Full cubeful rollout with variance reduction

36 games, rollout as initial position, Mersenne Twister dice generator with seed 2147483647

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.

 

Regards,

Ian