Author: Vincent Diepeveen
Date: 15:54:39 07/23/03
Hello,
Dr. Hyatt suggests to compare the difference between using big hashtables and
small hashtables in order to see how much of the system time is going to
hashtables.
In itself not such a bad idea under a few conditions
a) Pawnhashtable should be put to 64KB at most
b) Hashtable should be put to around 64KB at most too
c) in not a single case the pawnhashtable should cause a cutoff
d) in not a single case the hashtable should give a cutoff nor
a bestmove to search first
So basically the hashtables get called but do not give cutoffs. It is trivial
that bigger hashtables mean higher cutoff %. Those cutoffs in itself are a very
small % (in case of transpositiontable) but they take care that the search
process searches in the same game space.
No one can deny this. Especially not Dr Hyatt. He has written similar
observations in old articles of himself in ICCA journal.
So complaining that the above conditions aren't fair won't help if this reveals
that using big hashtables is quite a bit slower than small hashtables.
For the big test conditions c and d as above apply and for
a1) I advice 32M for pawnhashtable
a2) i advice 768M for hashtable
This basically only measures the influence of hashtables. Not even from the big
rotated bitboard move generation which is a megabyte or so if not more in size.
Note that this experiment is giving just a part of the truth. Just hashtables.
There is very good tools to exactly measure the real price one pays to RAM. One
of them you can download for free. If you have intel processors then intel has
stuff for free to download, if you have AMD processors then AMD has stuff of his
own too.
Best regards,
Vincent
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