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Subject: Re: Is more hash better? My tests say the opposite...

Author: Ed Schröder

Date: 01:28:04 09/01/03

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On August 31, 2003 at 19:44:28, William Penn wrote:

>The more hash I allocate, the slower the kN/s speed. Thus 4MB (the minimum) is
>the fastest in my tests, typically about 450kN/s. If I increase that to say
>256MB hash, the speed slows down to about 400kN/s. The more I increase hash, the
>slower the kN/s speed.

Correct observation, reasons:

1) more HT lookup's and updates.

2) Spoiling the processor's DATA cache.

Ed


>The kN/s speed peaks, then eventually starts to decrease. How long this takes
>depends on the amount of hash. However in my tests, the long term speed
>advantage of bigger hash never catches up with the long term speed obtained with
>smaller hash. Thus I don't see any advantage whatsoever to using a hash table!
>The opposite seems to be true!?
>
>I'm using the Shredder7 GUI, Shredder 7.04 UCI engine, AMD XP Athlon 2400+/640MB
>RAM (608MB available). The GUI says the maximum I can allocate to hash is about
>455MB, so I'm not near the limit. Of course I'm using fairly common practical
>positions for these tests in Infinite Analysis mode, and the above indicated
>results are typical.
>
>I get very similar results running Shreddermarks with different size hash. The
>more hash, the lower the Shreddermark and corresponding kN/s.
>
>Now, will someone please refute this, or explain what I'm missing or
>overlooking? Thanks!
>WP



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