Author: Gerd Isenberg
Date: 10:15:09 11/19/02
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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
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