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Subject: Re: Hash effects on knowledge vs. search

Author: Robert Hyatt

Date: 10:52:46 11/14/97

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On November 14, 1997 at 12:56:37, Johanes Suhardjo wrote:

>On November 13, 1997 at 22:35:43, Robert Hyatt wrote:
>>I'd like to see data on this topic.  For example, in a typical opening
>>or middlegame position, 30% hash hits is *very* good.  there is *lots*
>>of stuff that is stored and *never* used again, due to the way the tree
>>is traversed.  I depend on the hash stuff a lot, but in normal
>>middlegame
>>positions I don't see any huge performance issues at all.  IE I don't
>>think
>>the difference between the biggest table I can use (96mb) and the
>>smallest I
>>ever use (1mb) is more than 10-15% at best.  Perhaps in endgames this
>>goes
>>up.  I'm going to try to run a small set of positions with various sizes
>>of hash tables to see what happens.  But I can't believe (except for
>>some
>>endings) that we are talking even 50% speed changes...
>
>On my program, I can't compare the results with different hash sizes
>because
>each hash size results in a different search size.  The bigger the hash
>table, the smaller the tree (I haven't reached the point of diminishing
>return yet because of limited memory I have).  Is this normal or am I
>doing
>something wrong?

generally normal.  larger hash tables can also make the tree bigger at
times, too.

The issue is "time to solution".  Run the test position with different
hash sizes and note the time to depth=N.  then you have something to
compare...



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