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Subject: Re: Formula for hash table size

Author: Bob Durrett

Date: 05:46:08 08/29/03

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On August 28, 2003 at 11:14:53, Gian-Carlo Pascutto wrote:

>On August 28, 2003 at 10:46:26, Peter Fendrich wrote:
>
>>Let's assume that I allocate 256Mb for a 30 minutes blitz game and have enough
>>RAM to do so. Then there will be "no" conflicts or overwrites to mention. The
>>hash table "hit rate" will be the optimal for my program. Now let's lower the
>>size to 128Mb. I will get the same hash table "hit rate" with less RAM. If I
>>continue to lower the size my "hit rate" will at some point start to decrease.
>>When distributing memory between main hash table, KingPawn hash table, Nalimov
>>cashe and other tables I would like to know in advance a reasonable priority
>>scheme.
>>This is only a problem when the allocated RAM is low enough to make conflicts.
>>For instance the KP hash table size can be set to a more or less fixed value >for all situations but at some point it is more optimal to use some of it for >the main hash table instead.
>
>I think requiring the user to input things like the pawn hash table size
>is rather silly. How should he know what a good value is? Why not let the
>engine determine a good value automatically? I think all professional programs
>do this.

That assumes that user choices have no relevance to the issue of optimal hash
table size.  However, my intuition is that optimal hash table size depends to
some extent on what the engine is being used for.  As an example, one might be
playing a game, using automatic post-mortem game analysis, or doing manual
post-mortem analysis.  [See my other bulletin in this thread for related
discussion.]

Bob D.


>
>Just enter the total size and let the engine figure out the distribution.
>
>--
>GCP



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