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Subject: Re: Are bitboards really faster on 64-bit hardware?

Author: J. Wesley Cleveland

Date: 10:07:25 11/07/03

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On November 06, 2003 at 15:55:10, Russell Reagan wrote:

>In this thread:
>
>http://www.chess-archive.com/ccc.php?art_id=310212
>
>Gian-Carlo Pascutto reported that his program, Deep Sjeng (compiled for 64-bit
>hardware), ran 70% faster on an Opteron, clock for clock. As far as I know, Deep
>Sjeng is not bitboard based.
>
>In this thread:
>
>http://www.talkchess.com/forums/1/message.html?325912
>
>Eugene Nalimov reports that Crafy (compiled for 64-bit hardware) gets 1,761,569
>nps on a 1.8GHz Opteron. On my 2GHz Athlon, Crafty gets 1,230,931 nps.
>
>(2.0 / 1.8) x 1,761,569 = about 1,957,298 nps on a 2GHz Opteron
>
>So, clock for clock, Crafty is 1,957,298 / 1,230,931  = 1.59 times faster (60%)
>on an Opteron, while Deep Sjeng was 70% faster. I suspect Eugene was using his
>magic unreleased compiler also, which probably produces faster executables than
>gcc. But that is speculation.
>
>So either Deep Sjeng is bitboard based, or the expected advantage that bitboard
>engines were going to get that non-bitboard engines were not going to get does
>not exist. Or I'm overlooking something else.
>
>Thoughts?

If you look at these results from www.spec.org,

http://www.spec.org/cpu2000/results/res2003q3/cpu2000-20030908-02472.html
http://www.spec.org/cpu2000/results/res2003q3/cpu2000-20030908-02502.html

which were run on nearly identical opteron systems, one 32 bit using Intel C
compiler, and the other 64 bit using gcc, the results are slower or only
slightly better for the 64 bit compiler, except for crafty, which is 33% faster.
The bitboard functions should make up nearly all the advantage of 64 bit code. I
find this speedup remarkable.




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