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Subject: Matevalues, hashtables and iterative deepening

Author: Erik Robertsson

Date: 04:25:42 11/30/01


I´ve been trying to correct some bugs wich occur when storing mate values in the
hashtable.

If the position is evaluated as a mate value at the end of an iteration in the
iterative deepening, I stop searching and execute the best move. In some
positions however, I find that due to finding positions in the hashtable it can
result in the engine alternating between two different mate variations ending in
a quite embarrassing draw by repetiton.

I've tried to solve this by not automatically stop the iterative deepening
unless I've found a shorter mate than found in the previous move. Is there a
better way of solving this? I remember reading something about this some year
ago, but cannot find it.

I use the draft = *infinity* for mates wich are not bounds which should result
in that most positions with mate should be in the ht in the next search. Maybe
it has something to do with the bounds, but I´ve tried Crafty's MATE-300 bound
and it sometimes result in getting the evaluation of the position as MATE-300.

This has kept me awake a few nights, please help or I will go insane.



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