Author: Gerd Isenberg
Date: 11:01:19 11/19/02
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On November 19, 2002 at 13:30:57, Christophe Theron wrote: >On November 19, 2002 at 13:15:09, Gerd Isenberg wrote: > >>On November 19, 2002 at 12:25:11, Gian-Carlo Pascutto wrote: >> >>>On November 19, 2002 at 11:35:24, Robert Hyatt wrote: >>> >>>>Bitboards have a bit of a performance advantage on 64 bit processors, >>> >>>Proof? >>> >>>-- >>>GCP >> >>Hi Gian-Carlo, >> >>I think that's evident. If the none bitboarders have to use implicite native >>data-width of 64 bit integers, they have to transfer 32 additional zero bits >>without any additional information for each integer access. Of course you will >>pack some data, but all the local ints... >> >>So the information density for bitboarders grows with 64bit-architectures >>relative to none bitboarders. That also effects register usage, and that's IMHO >>more important. On x86-32bit architectures you can only hold three bitboards in >>registers, and thats even most a hard task. Actually, if you have a local >>routine with three bitboards and a few ints on the stack, there are a lot >>register/memory moves. Simply the data-width doubles the number of bitboard >>registers, not considered the increase in general purpose registers, or with >>hammer the number of mmx- and 128-bit xmm registers. >> >>Whether a bitboard based program is stronger than a none bitboard program >>depends obviuosly also on other things, but in principle :) >> >>Cheers, >>Gerd > > > >You have just explained why the bitboarders are less handicapped on 64 bits >machines. Hi Christophe, Yes. > >You have not explained why they are supposed to have "a bit of performance >advantage on 64 bits processors". > Ok, because they are less handicapped on 64 bit machines :-) Since Steffan Westcott teached me Flood-Fill- and Kogge-Stone algorithms here in CCC, and i tried my first mmx-implemetation without rotated bitboards, i believe that this attack/move generation routines are absolutely great for 64-bit processors with a lot of registers. I found bitboards the most natural data structure to define chess related patterns - and i like it. May be a individual matter of taste. Cheers, Gerd > > > Christophe
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