Author: Vincent Diepeveen
Date: 12:04:15 11/19/02
Go up one level in this thread
On November 19, 2002 at 14:34:21, Robert Hyatt wrote: Significant is that you first slow down your thing 2 times at a few points in order to get 33% faster later at the same points you first got 2 times slower. Anyway, by the time we all have 64 bits machines writing chessknowledge in bitboards is too cryptic anyway. Programming in a neat general way is always preferred above the bitboard hacking with inline assembly and things like writing only simplistic 1 line patterns IMHO. Best regards, Vincent >On November 19, 2002 at 14:24:04, Vincent Diepeveen wrote: > >>On November 19, 2002 at 14:11:18, Robert Hyatt 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 >>> >>>Counter-proof? >>> >>>Seems intuitively obvious to me. Bitmaps seem to suffer _no_ performance >>>penalty on >>>X86 with 32 bits, compared to 0x88. Seems intuitively obvious to me that they >>>will pick >>>up speed on a machine that does 64 bit operations. >>> >>>Bruce and I did this comparison when he used the alpha in the WMCCC (1997 I >>>think). >>> >>>He re-compiled ferret for the alpha, did the same for Crafty. My speed >>>improvement was >>>significantly better than his on the _same_ machine. Because of the 64 bit >>>stuff. His program >>>didn't need any 64 bit stuff so it was wasted... >>> >>>Best "proof" is to try it. I have... >> >>But at that time i also proofed that you generated moves already 2.2 times >>slower than i did. If you then get 33% faster because of getting 64 bits, >>that doesn't proof anything. > >OK... let's pick a common architecture and generate moves from a position you >choose. What processor/speed do you want to use? I have a bunch here, from >400mhz >to 550 to 700 to 750 to 800 to 1.4ghz that I can get to easily. > > >> >>If we look at the speed at specint of crafty versus specint of K7, >>then we see that a 1Ghz alpha 21264c, which is their fastest CPU, >>is performing at the OFFICIAL benchmark like a 1.33Ghz K7. >> >>So if we roughly give you 33% for bitboards going from 32 to 64 bits, >>then that's simply the maximum you can claim for it. > >33% is significant, is it not??? > >And I get it _free_... to boot... > > >> >>The argument that specint is not allowing inline assembly is not valid. >>I do not use inline assembly in my program either (with exception of >>locking at the x86). So let's keep it a fair compare. >> >>So first a slowdown of a factor 2 (used to be 2.2) then winning back >>33% because of getting 64 bits, that isn't very impressive to me. > > >I know. 10% is impressive when you want it to be. 33% is not when you don't >want >it to be... > >When we had the discussion about null-move not hurting SMP performance, it >dropped >from 3.1x faster to 3.0 faster when null-move was turned on. That was >significant to >you. When we had the speedup discussion where I said Crafty was 1.7X faster on >a dual >and you said it was 1.6X faster, that was significant. But 1.0 vs 1.3 is not >significant, >because you don't want it to be??? > > > > >> >>It sure is intuitively VERY CLEAR to me that just >>having 1 bit of info spreaded over loads of bitboards is not >>a very good plan, because for any complex chess pattern you >>simply need more instructions than non-bitboarders do. > >It might be clear to you. Fortunately, for those of us doing this stuff, we are >not quite >that rigid in our thinking, and we find solutions to problems that you say can't >be solved. > >The flood-fill stuff was one interesting discussion that you will have a hell of >a time doing >in a non-bitboard program... there are other cases where bitmaps might be >worse. But there >are just as many where they are better. As I said I don't see _any_ advantage >except that on >64 bit machines they are faster due to increased data density.
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