Author: Anthony Cozzie
Date: 09:16:24 09/03/03
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On September 03, 2003 at 11:45:32, Dezhi Zhao wrote: >On September 03, 2003 at 10:34:52, Anthony Cozzie wrote: > >>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. > >OK. But with SSE you have less overhead than MMX. >And using one or two xmm registers will help reduce register pressure. >I know the regular xor operations are fast. However you need at least two 32-bit >registeres to handle a 64 bit integer. When the hash calculation code is embeded >into probe code, you may end up with register spill over. > Feel free to try it, and if you get good results let me know :) anthony
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