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Subject: Problem with a long distance mate

Author: TEERAPONG TOVIRAT

Date: 20:54:03 04/16/02



Hi,

I've one problem. In a few specific conditions, my program shows
a strange behavior. For instance, when it sees a mate in 8-9 moves,
it follows the best line until only 2-3 moves left then it diverts itself
from the best line. This problem arises in the following conditions.

1.It's a long distance mate.
2.The superior side has only few minor pieces without any pawn.
3.The inferior side has only one king and is cornered.
4.It seems that the problem can be solved by clearing all hashtable
contents before each Search_Root() call. Not quite sure really.

IMHO, it's possible that the value stored in the hashtable in not the
best one because of collisions. For example, Nc3 to e4 is the best
move to mate,the program may move Nc3->d5->f6->e4 instead.
So,the retrieving mate score may be lowered by two plies.
I'm not sure about this explanation. Anyone has this problem before?
The best way to fix is?

Thanks for any help,
Teerapong



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