Author: Guido Schimmels
Date: 07:27:07 06/02/98
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On May 30, 1998 at 09:56:25, Robert Hyatt wrote: >there are at least a couple of things that could make Fritz far more >sensitive to hash table size than other programs: > >(1) a poor replacement strategy. If this is true, then a larger table >reduces replacement, which would produce better performance. > >(2) using the table for other things besides the normal score/best move/ >etc. If this is true, replacing *any* entry could be bad, depending on >what is stored in the table. > >no one knows what Fritz does, but one of the above reasons is almost >certain to be correct. I'd suspect (2) myself, since replacement >strategies are well-known now. Hi Bob ! Thoughts on (1): I heard, when the hashtable is only %60 full, Fritz5 already starts to suffer seriously. Sounds like poor replacement strategie to me. Remember Fritz5 is 200,000 nps on Pentium MMX 200. A single instruction added to such a fast program causes measurable slow down. Sophisticated replacement would drop that number significantly - at least if he does q-search hashing which I think he does - Frans Morsch may think, RAM is cheap, it's not worth it. Thoughts on (2): Maybe he stores some carefully chosen flags, who knows. But Fritz uses 64-bit entries (32-bit key / 32 bit move|score|depth|flags I guess), so not much bits left - if any - - Guido
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