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Subject: Re: Search Stability - ways to improve?

Author: Fabien Letouzey

Date: 02:35:34 07/02/04

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On July 02, 2004 at 04:14:50, Steve Maughan wrote:

Hi Steve,

>Yes this is what I currently do.  The situation that I'm concerned about is when
>I have a tactical position where, for sake of argument, the key move is Bxg6+.
>Monarch fails high on Bxg6+ at ply 7 only to fail low on the research.  The same
>is repeated at plys 8 and 9 until it find the solution at ply 10.  Clearly
>Monarch is "seeing" something at ply 7 but is not able to resolve it until ply
>10 - this seems a bit odd - probably a bug of some sorts.

Oh I see.  Now it looks like you analyse shorter lines during the
re-search than during the null-window search (e.g. because of
window-sensitive extensions).  For non-pure extensions (like
recaptures) you might want to try adding an "extend" flag in the
transposition-table entries, so that extensions are made consistent.

Note that I am not saying it would be a bug, many engines seem to
successfully use non-pure extensions without caring for search
inconsistencies at all.

>Having make the original post I'm thinking that the bug will most likely reside
>in the hashing code.  That's the first place I'll look.

Check your extension code first.  You can also test without the
transposition table, but then path-dependent decisions cease to be a
potential problem.

Fabien.




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