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Subject: False hash probes in endgame and how to avoid this problem

Author: Sergei S. Markoff

Date: 14:38:00 02/01/03


Hello All!

False hash probes in endgames is well known problem of the classical search
scheme. Same position can be the result of move chains which has a different
lengths. It causes the misevaluation because of the 50 moves rule.

The one idea is to use some multiplier N when evaluating position in which
50-moves rule counter is large. Fur example when this counter shows 50 plies we
can multiply evaluation onto 0.6 (or other value <1). Also we'll try to save
50-moves rule counter in hash entry and use this value to recalculate hash
evaluation.

I'm not implement this scheme at present but I'll try it in future. Are you
tried it? Or you have other non-secret approaches? I see that Ruffian is safely
avoiding this problem (see exact Ruffian evaluation in some positions, which is,
I think, not based on knowledge, for example: black: kh1, ph2, ka7; white: kf1,
wtm) (Fritz7 also shows 0.00, but immediately, I think it's because of specific
knowledge).

Sincerelly yours,
Sergei



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