Author: Roberto Waldteufel
Date: 10:14:36 10/01/98
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On October 01, 1998 at 08:12:57, Robert Hyatt wrote: >On October 01, 1998 at 01:58:58, Georg Langrath wrote: > >>If 32 bits are more effective than 16, does this go on? I mean are 64 bits >>better than 32, 128 bits better then 64 and so on. What is the optimum? >> >>Georg > > >Easy question. The optimum word size is the word size that moves around >the exact number of bits you need. IE in crafty, everything is based on >64 bit words, so 64 bit machines are more effecient for me. 128 would >buy nothing for me without some re-design... Hi Bob, Would it not be possible to improve efficiency a lot by doing two 64-bit operations in a single instruction, like MMX does two instructions at once on pentiums? Or you could use all sorts of new data structures, like an "etended" bitboard that allows four different settings per square. Certainly you would need to rethink some design issues, but I bet you would find ways to make use of all those extra bits, and even if you didn't, your compiler might find ways to optimise for 128 bits all on its own. I think the more bits, the better the possibilities, but it needs careful design to make the most of what you have available. Look how long it took for software to really start using the full 32-bit instruction set on the intel processors, and even now there is a lag with respect to MMX usage on pentiums. I find the most difficult aspect of code optimisation has been the operating system (Windows), which I do not properly understand, so I find it hard to figure out efficient ways to use memory, but for actual nuts-and-bolts stuff like writing an evaluation function for example, it pays to use assembler and make maximum use of the (few) registers available. When I program in assembler I have dreams about bigger registers...:-) Roberto
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