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Subject: Hashing is a complicated affair ?

Author: rasjid chan

Date: 09:54:30 04/05/04



I think most chess programmers implement hash tables my way, ie
by thinking it thru themselves. All the internet articles I found
about hashing only mention the the bare idea of hashing. I am not sure
whether any book on chess programming devote a full chapter on hashing
and if they do, what details do they provide.

I remember a certain professor (Marsland) who wrote something like...
the bulk of chess programming bugs come from hash-tables....
alpha-beta interacts with hash-tables in strange ways...

At least they interact strangely for me. Every a little while, it seems
something new turn up and I just have to post one example, a recent
observation,to this forum to be safe that I am not way wrong !

I do fail soft and fails / hash outside window bounds.
If on a hash probe and the hash is EXACT and fails high,
I return hash value ( > beta). The ply below fails low with
this "exact score".

If after seaching all moves of a node and it fails low with a best-score
< alpha, the normal hash is hash as best-score as upper bound.
But if this best-score happen to be "exact", I fail low but hash as
EXACT.

Hope I am not missing something big ?

Rasjid



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