Hi all, this bug in in the bug-tracker on gnubg.org, but it looks
so huge to me that it's maybe worth checking if anybody is having
a look at it.
GNU Backgammon Position ID: GwAAYAMAAAAAAA
Match ID : cAkFAAAAAAAA
+24-23-22-21-20-19------18-17-16-15-14-13-+ O: gnubg
OOO | O O | | | 0 points
OO | O O | | |
OO | | | |
OO | | | |
OO | | | |
| |BAR| |v (Cube: 1)
XX | | | |
XX | | | |
XX | | | |
XX | X X | | | Rolled 21
XXX | X X | | | 0 points
+-1--2--3--4--5--6-------7--8--9-10-11-12-+ X: MaX
A hint says :
1. Cubeful 2-ply 2/off 1/off Eq.: +0.722
86.1% 0.0% 0.0% - 13.9% 0.0% 0.0%
2-ply cubeful prune [world class]
2. Cubeful 2-ply 2/1 2/off Eq.: -1.000 ( -1.722)
14.4% 0.0% 0.0% - 85.6% 0.0% 0.0%
2-ply cubeful prune [world class]
Notice that after 2/1 2/off, player 1 will double out player 2
(hence the equity of -1.000).
Now selecting the two moves and doing a rollout we get the same result
(equities of +0.722 and -1.000) in the GUI version, but a different
result in the command-line (CLI) version : it gives equities of +0.722
and -0.713. As pointed out by the person that reported the bug (Philippe
Michel), -0.713 is the cubeless equity.
It is not a coincidence, since the same behavior appears for the following
position :
GNU Backgammon Position ID: GwAAYAsAAAAAAA
Match ID : cAkFAAAAAAAA
+24-23-22-21-20-19------18-17-16-15-14-13-+ O: gnubg
OOO | O O | | | 0 points
OO | O O | | |
OO | | | |
OO | | | |
OO | | | |
| |BAR| |v (Cube: 1)
XX | | | |
XX | | | |
XX | | | |
XX | X X | | | Rolled 21
XX | X X X | | | 0 points
+-1--2--3--4--5--6-------7--8--9-10-11-12-+ X: MaX
Here, no matter the move, player 1 is gonna double out player 2 next turn.
While GUI version correctly shows equities equal to -1.000 after a rollout,
CLI version shows cubeless equities ...
(MaX) hint
1. Cubeful 2-ply 2/off 1/off Eq.: -1.000
12.0% 0.0% 0.0% - 88.0% 0.0% 0.0%
2-ply cubeful prune [world class]
2. Cubeful 2-ply 3/off Eq.: -1.000 ( +0.000)
12.0% 0.0% 0.0% - 88.0% 0.0% 0.0%
2-ply cubeful prune [world class]
3. Cubeful 2-ply 2/1 2/off Eq.: -1.000 ( +0.000)
9.6% 0.0% 0.0% - 90.4% 0.0% 0.0%
2-ply cubeful prune [world class]
4. Cubeful 2-ply 3/1 2/1 Eq.: -1.000 ( +0.000)
0.0% 0.0% 0.0% - 100.0% 0.0% 0.0%
2-ply cubeful prune [world class]
(MaX) rollout =1 =2 =3 =4
1. Rollout 2/off 1/off Eq.: -0.761
12.0% 0.0% 0.0% - 88.0% 0.0% 0.0% CL -0.761 CF -0.761
[ 0.0% 0.0% 0.0% - 0.0% 0.0% 0.0% CL 0.000 CF 0.000]
Truncated cubeful rollout (depth 11) with var.redn.
648 games, Mersenne Twister dice gen. with seed 1036242101 and
quasi-ran
dom dice
Stop when best play is enough JSDs ahead: limit 1.96 (min. 144
games)
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]
2. Rollout 3/off Eq.: -0.761 ( +0.000)
12.0% 0.0% 0.0% - 88.0% 0.0% 0.0% CL -0.761 CF -0.761
[ 0.0% 0.0% 0.0% - 0.0% 0.0% 0.0% CL 0.000 CF 0.000]
Truncated cubeful rollout (depth 11) with var.redn.
648 games, Mersenne Twister dice gen. with seed 1036242101 and
quasi-ran
dom dice
Stop when best play is enough JSDs ahead: limit 1.96 (min. 144
games)
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]
3. Rollout 2/1 2/off Eq.: -0.809 ( -0.048)
9.6% 0.0% 0.0% - 90.4% 0.0% 0.0% CL -0.809 CF -0.809
[ 0.0% 0.0% 0.0% - 0.0% 0.0% 0.0% CL 0.000 CF 0.000]
Truncated cubeful rollout (depth 11) with var.redn.
144 games, Mersenne Twister dice gen. with seed 1036242101 and
quasi-ran
dom dice
Stop when best play is enough JSDs ahead: limit 1.96 (min. 144
games)
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]
4. Rollout 3/1 2/1 Eq.: -1.000 ( -0.239)
0.0% 0.0% 0.0% - 100.0% 0.0% 0.0% CL -1.000 CF -1.000
[ 0.0% 0.0% 0.0% - 0.0% 0.0% 0.0% CL 0.000 CF 0.000]
Truncated cubeful rollout (depth 11) with var.redn.
144 games, Mersenne Twister dice gen. with seed 1036242101 and
quasi-ran
dom dice
Stop when best play is enough JSDs ahead: limit 1.96 (min. 144
games)
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]
Pretty scary to me ...
MaX
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