[Bug-gnubg] MET and extrapolation bug ?

[Øystein Johansen]

GNU Backgammon  Position ID: Zg74CRCzmcGAJA
                    Match ID   : cAlgAnAAGAAA
    +24-23-22-21-20-19------18-17-16-15-14-13-+  O: GNU Backgammon
    | X  O  X  O  X  O |   |                X |  7 points
    |    O     O     O |   |                X |
    |                O |   |                  |
    |                  |   |                  |
    |                  |   |                  |
    |                  |BAR|                  |v 19 point match (Cube: 1)
    |                  |   |                6 |
    |                  |   |                O |
    |                  |   |                O |
    | X     X  X     X |   |    X           O |  On roll
    | X  O  X  X     X |   |    X     O     O |  3 points
    +-1--2--3--4--5--6-------7--8--9-10-11-12-+  X: Oystein


Hi,

The above position was posted to GammOnLine some days ago. As Albert replies
in one of his posts:

If a MET up to 15 is used, and GNU will use extrapolation from further scores,
the 2-ply evaluation says Double/Take. If I use Jacobs table, which goes to
25-away, GNU evaluates the position as a clear pass.

Please look at the numbers as the difference is so high that I suspect there
is a bug somewhere. ( Maybe a bug in the extrapolation algorithm? )

-Øystein