Author: Dann Corbit
Date: 17:31:16 01/13/03
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On January 13, 2003 at 20:17:36, Russell Reagan wrote: >On January 13, 2003 at 18:30:05, Matt Taylor wrote: > >>I think the real bottleneck would be the misjudgement of the speed of MMX. It is >>not as fast to respond as the integer units, though it maintains similar >>throughput. Using MMX for 64-bit arithmetic is not worthwhile as the same >>operations are available from the integer unit with lower setup costs. The only >>advantages include a minor gain in parallelism in hand-tweaked code and >>additional register space. > >Apparently if you use MMX correctly, it will be significantly faster than the >corresponding routine written in C (if it relies on 64-bit operations). The >primary example that comes to mind is that Gerd uses MMX in IsiChess to do >64-bit operations in the KoggeStone algorithms. He said it gave him a small >speed increase. Compare that with the same routines written in C, and the C >routines will be significantly slower. I know this because I wrote a program >using those routines in C and it got about 70 knps (compare with Crafty >300-500knps), and all it did was alpha-beta, material + mobility eval, and >nothing else. I tried several bitboard implementations, and the common factor in >the slow ones was the C KoggeStone attack generation. Gerd didn't experience >such a significant speed hit when he used his MMX routines. So it does appear >that there is a misjudgement of the speed of using MMX, but I'm not sure whether >it is an underestimation or overestimation. Can you post the slow C routine? I would be curious to see if it can be accelerated somehow.
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