Author: Scott Gasch
Date: 14:09:32 10/03/05
Go up one level in this thread
On October 02, 2005 at 13:49:37, Will Singleton wrote:
>White wins easily by promoting and exchanging queens, but most comps can't see
>it.
>
>[d]8/5p1P/8/8/6K1/5P2/1k6/q7 w - -
>
>Amateur failed to exchange queens, and drew the game. I'm not quite sure why,
>seems like a simple search should be enough to handle this. Oddly, if the
>exchange is forced, the win is seen immediately. This happens with other progs
>as well. I thought I had taken steps to eliminate root-position dependencies in
>the search, but maybe something else is happening.
One possibility is this: it's possible to win the f7 pawn if you promote and
don't exchange queens. So the engine is given the choice between KP vs. KP with
one king out of position and KQP vs KQ. The latter is preferable until the
depth gets deep enough to see the KP vs. KP is really a won KP vs K. I guess
the trick is to see that the KP vs. KP is won for the in position king:
[D]8/5p2/8/8/6K1/5P2/8/k7 w - - 0 0
--- WHITE -------------------LOC--VAL---- BLACK --------------------LOC--VAL-
PAWN:
---------------
centrality f3 5 target/isolated pawn f7 -9
target/isolated pawn f3 -9 pawn duos - 0
pawn duos - 0 exponential doubled - 0
exponential doubled - 0 exponential isolated - -3
exponential isolated - -3
TOTAL WHITE . . . . . . . -7 TOTAL BLACK . . . . . . . -12
KING:
---------------
centralize king g4 15
in/out of "action" g4 84
TOTAL WHITE . . . . . . . 99 TOTAL BLACK . . . . . . . 0
Static eval: +1.04
Scott
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