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Subject: Re: Finding mate in the quiesce search

Author: Tord Romstad

Date: 08:32:28 08/24/04

Go up one level in this thread

On August 24, 2004 at 10:56:13, Alessandro Scotti wrote:

>On August 24, 2004 at 10:50:07, Álvaro Begué wrote:
>>>I tracked the cause to the quiescence search returning mate, where it doesn't
>>>actually explore all the possible variations.
>>Your diagnostic is incorrect. There is no problem with returning mate scores in
>>the quiescence search. You must be doing something else wrong.
>If I evaluate a position using the quiescence search and that returns "mate in
>5", how can I be sure that it's really a mate in 5 if the quiescence search
>hasn't explored all the possible moves?

It sounds like you have forgotten to allow the return of "stand pat" scores
in the qsearch, or something similar.  If you are at a qsearch node where the
side to move is not in check, and all the moves you search are refuted by a
mate, you shouldn't return the mate score, but the stand pat score.  The only
way the qsearch can possibly return a mate score is if the side to move at
the first ply of the qsearch is in check, and all legal check evasions are
refuted by a mate.  And in this case, of course, you *can* be sure that it's
really a mate in x moves.


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