Author: Tom Kerrigan
Date: 14:08:24 03/28/03
Go up one level in this thread
On March 28, 2003 at 10:48:23, Robert Hyatt wrote: >On March 27, 2003 at 17:33:44, Tom Kerrigan wrote: > >>On March 27, 2003 at 15:57:20, Bernardo Wesler wrote: >> >>>Hi all: I have never received a concrete answer about this amazing three (lets >>>say) parameters regarding the "final' performance of an engine. >>>Ram memory, hash table and processor speed. >>>A concrete example and my non answered questions: >>>PC pentium 4, 1.8 Ghz; ram 512; windows xp pro.; Chessbase GUI; blitz games 15 >>>min per side; 4 man Tbs. >>>The most hash table size I put, the less processor speed i get? I mean if i put >>>64 mb hash table, does the processor run faster than if I put 388? and therefore >>>i obtain a better result from the chess program? >>>You realize that I definitively want to know if anybody can help me out (him by >>>himself or referring me to issued articles)to find out the best settings between >>>my hardware and a chess program in order to get the best results from it. >>>Thank you very much. >> >>There was a thread recently about how the amount/speed of RAM you have does not >>affect most chess programs. (Or at least it does not affect one of the more >>memory intensive programs, Crafty, except in a bizarre case with Eugene's >>Itaniums.) > >I didn't see this particular thread. Several ran a test a few years ago >starting with a >small (very small) hash table and going in several increments to a very large >one. The >typical middlegame speedup was about a factor of _two_. > >IE a hash table of (say) 16K entries vs a hash table of 16M entries. The NPS >didn't >change much at all, and actually goes down just a bit usually, but the time to >depth >can speed up by as much as 2x depending on how small you start at. You're talking about hash tables, I was talking about RAM. >>Hash table size does not affect processor speed, but it can affect the NPS you >>search (there's a difference). As soon as your hash table exceeds a few >>megabytes, though, it will not affect your NPS. Increasing hash table size gives >>you rapidly diminishing returns. I remember running tests where anything over 16 >>or maybe 32MB only gave me a percent or so of benefit (in terms of times to >>solutions, not NPS). But unless you need your memory for something else, you >>might as well set your hash table to the maximum size possible before you start >>thrashing (i.e., your hard drive going nuts because you don't have enough >>physical memory and you have to use virtual memory). > >The simple rule is that the hash table needs to be at _least_ large enough to >hold the >entire tree. Beyond that there are still gains due to the fact that the hash Or what? Your program will play illegal moves? -Tom
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