Author: Gerd Isenberg
Date: 02:48:14 08/11/04
Go up one level in this thread
<snip> >What I said was this: Hsu and I had a "discussion" about SEE vs MVV/LVA in >rec.games.chess.computer. I claimed that SEE was better, he claimed MVV/LVA was >just as good. > Fine that this discussions are still available via google group search! Very interesting reading. http://groups.google.de/groups?hl=de&lr=&ie=UTF-8&threadm=jwes.809762643%40BIX.com&rnum=22&prev=/groups%3Fq%3D%2522Feng-Hsiung%2BHsu%2522%26hl%3Dde%26lr%3D%26ie%3DUTF-8%26start%3D20%26sa%3DN >I first modified Crafty's q-search and normal search so that it used MVV/LVA to >order captures (there was a version or two of this released so that others could >run the tests as well). This version could _not_ prune captures as MVV/LVA >doesn't give enough information to decide whether a capture loses or wins... IE >if the largest piece hanging is a rook, and the smallest attacker is a queen, >MVV/LVA tries QXR first, whether the rook is defended or not. > >I then modified the normal crafty to use SEE but without excluding losing >captures, since MVV/LVA q-search had to try all captures for safety. > >I compared the two and found that SEE produced 10% smaller trees (this was on a >fast machine for significant searches) but was 10% slower, meaning there was no >advantage for either. > >Then I turned my original quisecence search pruning back on, something that >works for SEE but not MVV/LVA and the tree size dropped by 50% over a test set >of positions. This was based solely on the idea of (a) no SEE losing captures >(no reference to alpha/beta or the infamous "delta pruning" I now use); (b) >after 4 plies of q-search, no "exchanges" (even trades) either. That was what >early Crafty did, copied from a simple CB q-search that I used after the normal >CB q-search gave up on checks and threats and went to a simple capture-only >search near the end of the variations. > >My current "delta pruning" approach is even more effective in eliminating >q-search nodes. It would be easy to turn it off to compare tree sizes of >course.
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