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Subject: Re: Expected Hash Hit Rate

Author: Michael Henderson

Date: 19:40:35 09/16/04

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On September 16, 2004 at 22:14:36, Stuart Cracraft wrote:

>I have two variables "ttprobes" and "ttmatches".
>
>When I attempt a hash table probe, I always
>ttprobes++.
>
>In the probe routine, if I get a match on the 64-bit
>hash key, I do ttmatches++.
>
>My question is, for a tier-1 replace always table in
>a standard null move R=2 searcher with material-only/pc-sq-only
>evaluation, what kind of hit rate percentage should I expect with the
>following calculation
>
>  ttmatches*100/ttprobes
>
>Is there some other hash-table-related statistic calculation I
>should be doing to see whether the hash table is contributing
>its fair share to the search.
>
>Thanks,
>
>Stuart

Usually it's around 20-30% in standard time control searches. 15-20% for hash
cutoffs.  I'm not sure about hash matching in 1 second searches but I would
think it's relatively high because there is not much overwriting.

Michael



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