Author: Anthony Cozzie
Date: 07:34:52 09/03/03
Go up one level in this thread
On September 03, 2003 at 09:47:07, Dezhi Zhao wrote: >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. none of which impacts anything that i said. >> 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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