Author: Dezhi Zhao
Date: 06:47:07 09/03/03
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On September 03, 2003 at 09:07:13, Anthony Cozzie wrote: >On September 02, 2003 at 16:52:24, Dezhi Zhao wrote: > >>Hi! >> >>I know that some programmers here have played with MMX/SSE/SSE2 quite a lot. I >>am wondering if the new SSE registers and xor op can beat the regular registers >>in calculating the hash key that are 64 bit operations. Have anybody tried this? >> >>Regards, >>dzhao > > Generally speaking the 64 bit mmx/mmx2 operations don't help chess programs >because mmx is on the floating point pipe; to transfer data between the integer >& floating point pipes is something like 5-10 cycles each way; or if you go >through memory you have store-load stalls of a similar amount. Plus, the >regular integer pipe is actually pretty fast at bitboard computations because 2 >32bit ANDs can go down the pipeline together. > Please note that the new 128 bit xmm registers are in a seperate file, and you do not need the emms instruction for SSE stuff. > It only makes sense if a significant amount of work is being done, like in >Gerd/Steffan's floodfill routines for example. Computing the hash key is a >*very* cheap operation: two (maybe 3) times per make_move, lookup a 64 bit table >value and XOR. > >anthony
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