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Subject: Re: Auto configurable hash table size?

Author: James T. Walker

Date: 15:59:21 06/27/99

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On June 26, 1999 at 10:28:07, Robert Hyatt wrote:

>On June 26, 1999 at 05:34:58, Lin Harper wrote:
>
>>      On reading posts re: optimum hash table sizes for various
>>    programs and time settings for them, I could'nt help wonder
>>    why these programs don't auto adjust their own hash size for
>>    the situation they find themselves in as the game progresses.
>>      For example, during the opening phase hash is not needed,so
>>    the program could only activate the hash when the book runs out.
>>    As the endgame approaches and transpositions become more likely
>>    then bigger hash would presumably be an advantage, the hash size
>>    could adjust itself upwards.
>>       This must have been all thought of by clever programmers before
>>    and rejected for some reason. Perhaps it's just not possible to
>>    do it or the benefit would be negligible?
>>       Just a thought, guys.
>
>1.  It is not possible to determine total memory on a computer when they
>support virtual memory.  And if you make the hash table too large, performance
>will die.
>
*************
Perhaps you are referring to Crafty and the fact it can be ported to many
different environments?  Every time I start my Chessbase
programs(Fritz,Hiarcs,Junior,Nimzo) the GUI reports how much memory I have and
how much is already configured for hash tables.  So this information is
available in Windows98 somewhere.
Jim Walker
*************

>2.  changing the size during the game is also not really great, becaue when
>you change it you would have to stop and 'relocate' all the entries, or else
>clear it.  Neither of which is worth the time spent.



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