Author: Colin Frayn
Date: 13:26:59 09/21/02
I've been messing around with Beowulf recently and I noticed that doing reduced depth NULL move searches where the depth is cut to less than one ply, and therefore the search continues directly into the Qsearch, tends to cause search problems. That is, that the search suddenly avoids the best move, or can't find it in the same number of ply, or else gets it and then fails (very) low on it. Without NULL moves going directly into the Qsearch, Beo doesn't make any of these mistakes on the positions that I've tested, and gets the correct move easily. Example positions are WAC 019, 116, 120. These are all easy positions, but sometimes when I've fiddled with the eval I find that suddenly they aren't solved any more. I'm wondering if there's any known tactical problems with this technique. I can't just switch it off because then I get a performance decrease (and a substantial one, too). Is this something to do with the fact that the Qsearch only returns an approximate score (because of the stand-pat algorithm)? Is there any way to make this safer? Does anyone else experience this? Cheers, Col
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