Re: [Bug-gnubg] Bug#659494: Resigns more points than necessary when fewer points would still result in opponent win

[Michael Petch]

As an addendum. Bots often make what seem like unnatural plays compared
with that of a human. If every decision has the same equity the bot will
use the one that happens to be at the top of it's decision list (And to
a human can seem random and odd). If we start going down this slippery
slope then the user will then ask us why the bot might do this (look at
what move the bot plays in this case. It doesn't save the gammon):

    GNU Backgammon  Position ID: AwAA2Lo7EAAAAA
                    Match ID   : 8AlnAaAAAAAA
    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: mpetch
OOO | O                |   |                  |  10 points
OOO | O                |   |                  |
OOO |                  |   |                  |
 OO |                  |   |                  |
 OO |                  |   |                  |
    |                  |BAR|                  |v 11 point match (Cube: 1)
    |                  |   |                  |
    |                  |   |                  |
    |          X  X  X |   |                  |
    | X  X     X  X  X |   |                  |  Rolled 61
    | X  X  X  X  X  X |   |                X |  0 points
    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: gnubg


    1. Cubeful 2-ply    12/6 4/3                     MWC:   0.000%
       0.0000 0.0000 0.0000 - 1.0000 1.0000 0.0000
        2-ply cubeful prune [world class]
    2. Cubeful 2-ply    12/6 3/2                     MWC:   0.000% (
0.000%)
       0.0000 0.0000 0.0000 - 1.0000 1.0000 0.0000
        2-ply cubeful prune [world class]
    3. Cubeful 2-ply    12/6 2/1                     MWC:   0.000% (
0.000%)
       0.0000 0.0000 0.0000 - 1.0000 1.0000 0.0000
        2-ply cubeful prune [world class]
    4. Cubeful 2-ply    12/6 1/off                   MWC:   0.000% (
0.000%)
       0.0000 0.0000 0.0000 - 1.0000 0.0000 0.0000
        2-ply cubeful prune [world class]
    5. Cubeful 2-ply    12/5                         MWC:   0.000% (
0.000%)
       0.0000 0.0000 0.0000 - 1.0000 1.0000 0.0000
        2-ply cubeful prune [world class]
    6. Cubeful 2-ply    12/6 5/4                     MWC:   0.000% (
0.000%)
       0.0000 0.0000 0.0000 - 1.0000 1.0000 0.0000
        2-ply cubeful prune [world class]


----

To a human, it may seem natural to save gammon - to the bot it knew it
was playing a lost cause so it decided not to even save itself from a
gammon. The bot knows it has no way to win, and that all moves have 0
equity. In this case the first move listed gets used which is 12/6 4/3
which gets the bot gammoned. The human win 12-0. But  a human might say
"hey wait a minute I should have only won by 11-0, what is the bot doing
it is unnatural not to save a gammon - a human likely wouldn't do that).

Same principle applies here. Bot doesn't care how much the human wins
by. A win is a win no matter the number of points you go over by. Should
there be an option that the bot must play to save gammons and
backgammons in lost causes (absolutely 0% chance to win)? I'd say heck
no, again pointless as the end result of a match loss remains unchanged.

-- 
Michael Petch
CApp::Sysware Consulting Ltd.
OpenPGP FingerPrint=D81C 6A0D 987E 7DA5 3219 6715 466A 2ACE 5CAE 3304