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Subject: Re: Efficient hash algorithm?

Author: Peter Fendrich

Date: 02:46:04 09/22/98

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On September 21, 1998 at 19:54:53, John Coffey wrote:

>On September 21, 1998 at 19:45:21, José de Jesús García Ruvalcaba wrote:
>
>>On September 21, 1998 at 19:35:39, William H Rogers wrote:
>>
>
>>>That is why I suggested a smaller hash key of only 16 bits. That gives you 64K
>>>which is a lot for a smaller program. Think about it 64 thousand opening book
>>>replys. But the other boy are correct, if you have the space.
>>
>>	What has to do the opening book with the hash tables? Are the opening book
>>positions stored in the hash tables somehow, at the beggining of the game?
>
>There is some confusion here.  *MY* questions about hash tables have to do
>with the posiition history for move searching.  But hashing can also be
>used as a way of storing opening moves.  It has the advantage that it
>recognizes transpositions.
>
>john coffey

Yes, and I think most answears are refering to what you're asking for but you
will find that this hash technique is useful in many ways.
 - Hashing nodes as discussed here
 - Hashing evaluated nodes and fast get the position evaluation instead of
   compute it over and over.
 - The same goes for pawn evaluation. You will be able to have heavy evaluation
   code for pawns and because the same pawn pattern will be repeted, hash it...
 - As entries in your opening book.
 - As entries in your learning file(s)
 - A fast way to discover 3 (or 2) times repetition of positions.
 - Probably more, I haven't mentioned...

//Peter



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