Author: Robert Hyatt
Date: 10:25:28 04/28/03
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On April 28, 2003 at 12:24:59, Charles Worthington wrote: >So am I to understand that the time control being played has nothing to do with >the correct hash size? It depends on your meaning of "nothing to do." If you make the hash size too big, all you do is waste memory, unless you go beyond memory size and into virtual memory and paging. However, there is always a "right" hash size for a particular program and processor speed. Going beyond the "right size" won't hurt, but it won't help, and it risks problems should you run another program that needs a lot of memory which will cause the chess program to start paging. >If time control is a factor (which I have always assumed >it to be) then isnt a too-large hash crippling because it forces the program to >search for a needle in a haystack when it could actually recalculate the >position faster than it can find it in a mostly-empty hash? We don't "search" thru the hash table. We do a direct probe and either find what we want at that position or we give up. So a big hash table doesn't hurt a thing from a speed point of view, so long as the program (a) does not clear the hash between every move, which would hurt in blitz games with a huge hash as it takes time to clear huge tables; (b) doesn't page because the hash size is too large for the machine. > I have been running >a 16 to 32 MB Hash on my dual 3,06 Xeon in 3+2 Blitz and 8MB in 1+0 Bullet. >128MB in 15+3, 256 in 30+5, 512 in 60min and so forth. These are close to what >the chessbase t-notes recommend. They say that too small is better than too >large and that if in doubt its best to err on the small side. Opinions on these >hash settings anyone? > Their suggestion is wrong (best to err on the small side). It is better to be too big rather than too small, so long as the two problems described above don't become an issue... >Charles
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