Author: Sune Fischer
Date: 08:13:37 06/27/03
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On June 27, 2003 at 11:00:56, Uri Blass wrote: >On June 27, 2003 at 10:46:08, Sune Fischer wrote: > >>On June 27, 2003 at 08:13:53, Albert Bertilsson wrote: >> >>>Just wanted to share my latest findings and warn you from making the same >>>mistake (or maybe I just point out the obvious). >>> >>>I've always been proud to have a very fast movegen, doing perft calculations >>>very fast. I optimized the movegen alot, and always saw playing strength >>>increasing. I use a legal move generator and always saw the cost of verifying >>>legality to be minor. Lately however I've noticed that the engine performance >>>isn't that great (compared to other engines) inspite of the fast movegen. So I >>>started digging today and the numbers struck me as lightning... >>> >>>As I've improved moveordering very much with hashtable/iterative deepening, >>>killer moves and history tables the effective BF is now much lower. The lower BF >>>now means that very few moves of all the generated ones are actually ever made. >>>This means that the cost of generating legal moves have increased incredibly >>>much. >>> >>>It's really anoying to notice that something you though was very good now is on >>>the list of improvements again =(. >>> >>>/Regards Albert >> >>What that saying with premature optimization being the root of all evil? :) >> >>Well it think it is correct, and probably a typical mistake to spend oceans of >>time optimizing one thing only. > >I do not think that the Albert spent ocean of time in optimizing. >Based on reading his posts I got the impression that he did not do it. Ah hmm, but I get the opposite impression. :) >His program is relatively fast in perft because his program has a different >structure(he use legal move generator when most of the programmers do not do >it). Perft is no good speed indicator anyway, not even for a move gen. The perft tree is so different from the chess tree. Optimizing for perft is basicly like building a formula 1 car to use for off-road rally. -S. >Uri
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