Author: Robert Hyatt
Date: 08:03:04 03/13/01
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On March 12, 2001 at 18:04:08, Dann Corbit wrote: >On March 12, 2001 at 16:09:46, Robert Hyatt wrote: >[snip] >>OK. I can't imagine how a program could be written to behave like that, but >>I assume it is possible since you saw it somewhere... >> >>In the case of Crafty, .1% is the right number. In the "main search loop" there >>is a single test/branch that is executed needlessly, once per node, for the >>SMP version when there is no extra processors being used. > >It depends a lot on what library functions are called. Sometimes, the SMP link >libraries are simply slower than the single threaded versions. I have >definitely seen this effect from time to time. > >Your program also has a very smart use of interlocked exchange which is a very >inexpensive form of synchronization object. If you used something else, there >could be a big penalty. That is possible. But in the case of a chess engine, I can't imagine it making very many library calls at all in the search. I know I don't...
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