Author: Robert Hyatt
Date: 22:07:45 05/26/04
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On May 27, 2004 at 00:55:26, K. Burcham wrote: > > >Bob if you were running Crafty with dual Opteron 248 at 2200 mhz in 90/30 game, >what would you set your hash at? > >if running 848, 4 x 2200 mhz in 90/30 game, what would you set your hash at? > >kburcham I think I would do this: 1. estimate the raw NPS. dual 248's will do from 4M to 6M nodes per second. 2. look at total RAM size of the machine. Take 3/4 of that. If you are going to play a long game, just set hash to 3/4 of memory and let that be it. If you are going to play on a chess server, use the adaptive command with the estimated NPS and a reasonable min hash size, with 3/4 of memory as the max, and let Crafty set the hash size. Note that since I don't hash q-search nodes, Crafty doesn't need as big a hash table as a program that does. You could look at the log files for the last CCT to see what I used. I really don't remember. I do remember that the machine had 8 gigabytes of RAM, 2 gigs per processor... Another way to do this is pick an opening, a couple of middlegame and an endgame position... set the time limit to the kind of game you are tuning for, then run the positions. I'd use just one CPU to avoid SMP variability. Keep increasing the hash size until the search times stop getting shorter. Going beyond this point is not going to help. If you have 4 cpus I would multiply the size by at least another factor of 2, or even 4, to account for the increased search tree size... If I get a chance, I'll take Crafty and run a set of 20 positions through it on my dual xeon, and vary the hash size from something like 3M to 3/4 gig, and post the search times... If you can double that NPS you should probably double that hash size... Note that a single 2.2ghz opteron is actually significantly faster than my dual xeon when you figure in the 30% loss (30% of one of the two processors). And even if you ignore that, the opteron will be slightly faster in raw NPS as well...
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