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Subject: What's optimal hashtable size for different time controls?

Author: Laurence Chen

Date: 05:39:56 04/15/00


Hi all,
   I've ran some blitz games between Junior6a and Rebel Tiger 12e, and Hiarcs
7.32 and Rebel Tiger 12e, and I was surprised the results. I'm using two
identical computers, Pentium III 600E, autoplayer 232, blitz games at 5 min. + 3
secs.  Junior and Hiarcs were using Fritz 5.32 opening book, and Rebel Tiger its
default book with NSEW=1, MoreSel=1. In the match where all engines were using
16 MB of Ram for hashtables, Rebel Tiger got trounced very badly, against Junior
6a, it lost to a score of 15.5-34.5, against Hiarcs 7.32, it lost to a score of
13-37.  Jim Walker suggested that I use 8 MB of RAM instead, so I ran another
match of Rebel Tiger against Hiarcs 7.32, both engines using 8 MB of RAM, and
now Rebel Tiger lost to a score of 21-29.  I'm sure there are dupes, but that's
Rebel Tiger fault for having a bug in the learning book. Yes, I downloaded the
patch for learning from Rebel's website, and it did not fix the problem.  This
clearly shows that giving more hashtable for Rebel Tiger in this time control is
very bad.  The engine performance goes down a lot.  So this raises the question,
what is the optimal hashtable for different engines at different time controls?
One cannot assume that 8 Mb of RAM for Hiarcs is better, I will later on run
another 50 games match with Hiarcs having 16 MB of RAM, and Rebel Tiger 8 MB of
RAM.  A lot of us think that more RAM increases the strength of a chess engine.
From this little experiment, it clearly shows that the opposite is true.  I
believe that there must be an optimal hashtable size where the engine will
perform its best when given the proper hashtable size for a specific time
control.  How would one figure this out?  I think that test suites cannot
provide a proper answer to this question, any ideas.
Laurence



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