Author: Vincent Diepeveen
Date: 12:49:27 02/03/04
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On February 03, 2004 at 12:15:23, Robert Hyatt wrote: >On February 03, 2004 at 11:45:20, Vincent Diepeveen wrote: > >>On February 03, 2004 at 03:13:29, Gerd Isenberg wrote: >> >>>On February 03, 2004 at 01:03:29, Jay Urbanski wrote: >>> >>>>On February 02, 2004 at 22:41:19, Robert Hyatt wrote: >>>> >>>>>On February 02, 2004 at 20:06:29, David Rasmussen wrote: >>>>> >>>>>>Does the Opteron have firstBit, lastBit and popCount instructions? Or at least >>>>>>something that makes calculating them easier than on x86-32? >>>>>> >>>>>>/David >>>>> >>>>> >>>>>Has the same BSF/BSR instructions, but no popcnt that I have found. Note >>>>>that BSF/BSR work on 64 bit values if you want. I have inline asm to do >>>>>all three for gcc if you are interested. >>>> >>>>I understand there is a popcount instruction. I also understand it's >>>>undocumented. >>> >>>Do you have any opcode or further hints? >>>That would be great - a 4 cycle vector path popcount ;-) >> >>And deadslow. > > >Certainly not slower than what we have to do at present... Yes it is slower, because no one ever thought of it in bitboards to write such stuff incremental. No popcnt's needed then. In fact majority of crafty's simple eval you can write incremental and it's way way faster. Note that i'm not doing evaluation incremental (some datastructures i do) in DIEP, because i am busy making a huge great evaluation function. Readability and portability above anything else! mixing 8 unsigned bits arrays such as several solutions for BSF/BSR replacements at opteron use with signed ints with unsigned long long mixed with unsigned int. I find it all very bad to do. It's trivial that i could get diep easily 10% faster at opteron by rewriting all 'int' arrays to 'unsigned int'. In that case at several spots in the program unsigned int gets mixed with signed. I find that detestable however. The same logics applies here to doing entire evaluation incremental in bitboards. You can throw away most of your bitboard logics of course as incremental stuff goes faster in non bitboards, but with or without bitboards, doing it incremental is *way* faster and you can avoid expensive stuff like pop counts.
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