Author: Robert Hyatt
Date: 17:33:16 02/19/03
Go up one level in this thread
On February 19, 2003 at 19:35:11, Eugene Nalimov wrote: >On February 19, 2003 at 18:20:16, Tom Kerrigan wrote: > >>On February 19, 2003 at 02:53:13, Matt Taylor wrote: >> >>>On February 18, 2003 at 13:33:12, Tom Kerrigan wrote: >>> >>>>On February 16, 2003 at 03:03:03, Matt Taylor wrote: >>>> >>>>>On February 15, 2003 at 21:28:39, Tom Kerrigan wrote: >>>>> >>>>>>They are if they better represent computer chess than Crafty does. I'd bet most >>>>>>chess programs out there don't use bitboards (i.e., 64 bit operations) or use >>>>>>bitboards less than Crafty. Bitboards are almost certainly the reason why Crafty >>>>>>performs well on I2 vs. the P4. >>>>>Perhaps it is, perhaps it isn't. Athlon is much more efficient with 64-bit >>>>>operations than Pentium 4 is, and the Athlon isn't pulling ahead by huge strides >>>>>(in Crafty). >>>> >>>>How do you figure the Athlon is more efficient? And what do you mean by >>>>operations? ANDing, ORing, etc.? How about loading, shifting, BSF, popcount, >>>>etc.? >>> >>>How about faster in MMX, faster in shifting, and faster in arithmetic? An MMX >>>implementation will be slower on the Pentium 4. Code written in C to do the >>>equivalent will involve much shifting and arithmetic which will also be slower >>>on the Pentium 4. As far as I can tell, the bsf instruction on P4 is not really >>>any faster than Athlon's, but it is hard to say. >>> >>>Logical ops have equal cycle counts on both processors making the P4's higher >>>clockrate advantageous; however, logical ops are hardly the only bitboard >>>manipulations. >> >>So the Athlon is much faster, except that it's the same for logical ops and bsf. >>And we apparently don't know if Crafty uses MMX, where the Athlon would have an >>advantage (what are the latencies of 64-bit MMX shifts on each chip?), or if it >>breaks the bitboards into 32 bit numbers and does "normal" operations on them, >>in which case I don't see why the Athlon would be any faster than the P4. (I'd >>be surprised if anything gets shifted by very much in Crafty so the P4's lack of >>a wide barrel shifter is probably not a handicap.) >> >>-Tom > >So please be surprised. Crafty contains lot of shifts by variable amount -- long >time ago I rewrote several hottest functions in the assembler, and they contains >lot of shifts. AttacksDiaga1Func(), AttacksDiagh1Func(), AttacksBishopFunc(), >MobilityDiaga1Func(), MobilityDiagh1Func(), AttacksRankFunc(), >AttacksFileFunc(), AttacksRookFunc(), MobilityRankFunc(), MobilityFileFunc()... > >Thanks, >Eugene Jeez. Forgot about the rotated bitmap stuff, you are right, it is done all over. I only thought about generating and evaluating pawn moves. All the move generation for "sliders" shifts like mad. :)
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