Author: Ralf Elvsén
Date: 19:48:26 12/19/01
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On December 19, 2001 at 14:18:21, James Swafford wrote: > >I'm just now getting around to implementing a null move search in >the dinky little thing I've been playing around with lately. > >One of the move ordering stats I keep track of is the ratio of >fail highs on the first mv vs. the number of total fail highs. >Previously this number has been at 87% for the first 100 problems >of the Win at Chess suite. (My eval is so simple I don't bother >testing more than that yet. :) ) > >With a pretty kludgy null search with R=2, I'm getting a few more >problems right, and searching a little deeper on average. An >observation I made, though, is that the ratio mentioned above fell >to 78% - a delta of 9%. > >At first glance that makes sense to me, though I'll have to think >about it a little more later. It leads me to wonder, though, >if this is consistent with more sophisticated engines. > >For those out there that keep track of that ratio, have you measured >it without a null search? I'd be interested in hearing the numbers >with and without the null search, just to be sure I didn't break >something. I have experienced the same problem. I still have to understand why. I thought it had to do with the killermoves, so I had separate killermove lists after zero, one, two nullmoves but that didn't make any difference. Please post here if you figure out how to cure it :) I use hashing, killers and SEE to order my moves. Ralf > >Most folks know that a null move can break things in zug positions, >so I'm left to wonder when it's a good idea to avoid it. In a >previous program, I used a simple measure of material. I think >I said if the material for the side to move was less than a rook, >avoid the null search. Something like that. Anyway, has anybody >come up with a better idea? > >I tried Vincent's "double null move" a couple years ago in Tristram, >and I found it to be pretty good. Anybody else using it these days? >(besides Vincent. :) ) > >-- >James
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