Author: Aaron Gordon
Date: 17:06:03 03/27/03
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On March 27, 2003 at 17:41:03, Tom Kerrigan wrote: >On March 27, 2003 at 17:20:02, Aaron Gordon wrote: > >>As far as speed goes.. if you use a very large hash table you can generally >>(depending on the chess engine) expect to see a 2-10% increase in nodes per >>second by doubling your ram speed (going from SDR to DDR for example). If you > >How did you get this data? Recently there were a number of posts about how >Crafty doesn't get any faster even if you quadruple RAM speed. I was the one that did most of that testing. Thats with Crafty using an extremely small hash table. With much larger hash tables you can expect to see a mild increase in nps from doubling your memory speed. Still the main thing in chess is processor speed. You'd get nearly a 100% speed boost from going to 2GHz from 1GHz as you said in your previous post. Now, for memory speed you may only get 2-10% doubling memory speed with large hash tables (256mb+). With sub-32mb hash tables you will see next to nothing, though. If I can find some of my older test results I'll provide them here. If I can't find them I'll just go ahead and retest memory speed vs massive hash table size. >>So far I have noticed with Fritz 5.32 set to 255mb hash gets filled entirely in >>about 1 minute at 2.5 million nodes/second on my AthlonXP 2.5GHz. > >It's not clear to me that the "fullness" of a hash table is a significant >metric. It's the usefulness of the entries in the table that counts. Do you get >better scores (or faster times to solutions) on test suites with really big hash >tables? > >-Tom I haven't done any test suite testing, just numerous games on FICS. With smaller hash tables it seems the engine just looses it's "oomph" after the hashtable is full. I see a LOT more draws when I use a hashtable 128mb or lower vs 256 and more. I mainly use Deep Fritz 7 and Fritz 8, so you may see some different results with other engines. Generally from what I've seen though when using a fast CPU with tons of hash the engine just seems to pack more of a punch. About the slower searching engines. I'm not too sure about their hashtable methods or whether using massive hash tables is best. I did notice in Shredder classic that the hash fills up a bit slower than Fritz 5.32 (can't measure w/ the newer Fritz engines). It was still fast enough though to make me want to keep the hash as big as possible.
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