Author: Anthony Cozzie
Date: 07:06:43 08/11/04
Go up one level in this thread
On August 11, 2004 at 05:48:14, Gerd Isenberg wrote: ><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. Writing a good q-search is just tough, and it is very important for null move pruning. Zappa's q-search is fairly reasonable right now, but it has a _long_ way to go . . . anthony
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