Author: José Carlos
Date: 05:46:06 01/05/01
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On January 05, 2001 at 08:28:07, Severi Salminen wrote: >>What is the best way to sort moves at the root after each iteration? > >I sort root moves so that PV comes first then other moves sorted by number of >nodes that were visited searching that particular move. There're many possibilities here, and the best one can do is try them all. What I do in Averno is: - The first time, I sort with my normal criteria (wining captures, etc...) - After that, every fail high at the root makes that move become the first of the list so, after, several fail highs, at the beggining of the list I have the last fail highs, the most recent first. >>What is the best way adjust alpha and beta at the root after each iteration? > >First I do a 1 ply search. Then I do search with 1 pawn wide window. Aspiration search usually uses the value from the previous search, istead of this 1 ply search. My AS window is 25 centipawn. >If I fail >high or low I do a research: score-1, INF (fail high) or -INF,score+1 (fail >low). The score is the score returned from the search that failed low or high >in >the first place. I do an intermediate try, adding/substracting 150 centipawns and only if that fails high/low again, use +INF/-INF. >Notice those +1 and -1. Without those you'll get fail lows and >highs again. I use fail soft and this means that you have to be sure what to >return from search, qsearch and evaluate. A wrong value returned from (say) >futility pruned node means problems. The point is that if you fail high or low >in the first search you have to be sure that the score returned is the other >bound of the true score. > >>I notice I sometimes when I get a fail low at the root, I do a research, and >>then get a fail high! The most likely explanation is that I am a moron and it >is bug. > >Well, we are all morons, so that can't be an explanation. But yes, it must be a >bug. Hashing and null move can very well cause this behaviour, not necessarily a bug. José C. >>Are there other issues that are important in the root position, or any "tricks" >>that one should know? > >Don't know. > >>Spank you. > >Oooh yeah! > >Severi
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