The score is: You 2, GnuBG 0 (match to 7 points)
Move number 4: GnuBG on roll, cube decision?
| You | 5 | ||
|---|---|---|---|
                  | |||
| GnuBG | 11 | ||
| Position ID: DQAA4AUAAAAAAA Match ID: UgngACAAAAAE | |||
• GnuBG doubles
This double really surprised me! But, I guess it's pretty simple? If GnuBG loses ATS, it's down 7away 1away. According to its match equity table it would only have 9.28% MWC, far less chance than putting the entire match on the line right now.
| Cube decision | |||
|---|---|---|---|
| 4-ply cubeless equity | -0.555 | (Money: -0.555) | |
| 0.223 0.000 0.000 - 0.777 0.000 0.000 | |||
| Cubeful equities: | |||
| 1. | Double, take | -0.532 | |
| 2. | Double, pass | +1.000 | +1.532 |
| 3. | No double | -0.555 | -0.023 |
| Proper cube action: | Redouble, take | ||
However...If I change the current score to 1 to 0, then GnuBG is down 7away 2away if it loses. Its corresponding MWC is 15.79%, still far below the 22.3% chance it has to win this game. But, it says that's a big error (-0.211) to double.
The score is: You 1, GnuBG 0 (match to 7 points)
Alert: wrong double ( -0.211)!
| Cube decision | |||
|---|---|---|---|
| 4-ply cubeless equity | -0.555 | (Money: -0.555) | |
| 0.223 0.000 0.000 - 0.777 0.000 0.000 | |||
| Cubeful equities: | |||
| 1. | No double | -0.555 | |
| 2. | Double, pass | +1.000 | +1.555 |
| 3. | Double, take | -0.766 | -0.211 |
| Proper cube action: | No redouble, take (12.0%) | ||
Further more, at the original score, several rolls previous to this position it had reached a 27.7% chance. But, 4 ply analysis said it'd be a -0.088 error to double.
So, what is it that this intermediate does not not grasp?
Thanks
ps- I'm using: Version GNU Backgammon 1.00.000-mingw 20130519.