Author: John Boyd
Date: 22:18:11 03/22/03
Hi All, I was reading Ed Schroeder's page on Rebel internals and saw his comment that it is not necessary to generate all captures in QS... only winning/equal ones... I quote... "Unlike other chess programs REBEL (since the esarly 80's) in QS does not investigate all captures, there is absolutely no need for that, it's pretty safe to search only the winning captures, equal captures (QxQ, RxR etc) and Queen Promotions. Minor promotions are also excluded from QS, it's a waste of valuable processor time. Excluded from the above are of course the situations when the king is in check, all moves are generated and searched. For a given ply in QS REBEL will first generate and search the winning captures, secondly when those moves do not cause a BETA cut-off then search the equal captures and thrid and last do the checking moves (this limited to a predefined depth, more later), the rest of the moves is skipped." Endquote Okay, so I thought I'd try this and found that it certainly made the search faster than a scalded cat... and it blitzed the Wacnew testset but when it played games it became much weaker than before... I noticed also that the search was more volatile ie. it now changed its mind a lot unless there was a definite win of material. Anyone else found this? Have I overlooked something? If this is relevant, I currently update the hashtable in the Qsearch and generate all moves when in check, otherwise, I generate only winning/equal captures and queen promotions as per Ed's suggestion. And there's no limit to the Qsearch recursion... Any help appreciated! Ross
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