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Subject: Re: RAM , Hash tbl. and processor speed

Author: Anthony Cozzie

Date: 15:59:13 03/27/03

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On March 27, 2003 at 17:20:02, Aaron Gordon wrote:

>The two main things you want to do is get a processor that is as fast as
>possible and with longer time controls use a hash table that is as big as
>possible. With 512mb try not to go above 384mb hash, any more and it'll
>definitely swap. 320mb is pretty safe to use. With 256mb ram 160mb hash is
>probably going to be your max.
>
>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
>use smaller hash tables (less than 32mb or so) you'll see no measurable
>difference. If you use 32mb hash vs 320mb hash w/ 512mb ram you'll generally see
>a slight drop in nodes per second. This is fine, though, because in long time
>controls a larger hash is much, much better.
>
>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.
>On FICS I use the computer account "LittleGoliath". For lightning games I use
>192mb hash, for short blitz games (3 0 to 4 1) I use 256mb hash, for blitz over
>5 1 I use 320mb hash and for standard games I use 384mb hash.
>
>Since your P4-1.8GHz is about the speed of an Athlon 1.2GHz it'd be wise to use
>about half of the hash I'm using except for long time controls. So, for your
>P4-1.8.. 96mb hash for lightning, 128mb for short blitz, 160mb for longer blitz
>and 384mb (or 320mb to ensure no swapping happens) for long time controls would
>probably be best. Just uset these hash sizes to start out with. You could get
>better results by experimenting with various sizes.. I wouldn't go below those
>settings much though.


One of the nice things about a larger table is that there are fewer collisions.

anthony



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