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Subject: Re: What approach do you use to handle castling/en passant for repetition?

Author: William Bryant

Date: 14:04:13 02/28/00

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I am curious,
do you hash a different constant for each of the 16 possible ep squares, or
simply a single constant if ep is possible.

I have sixteen different values that are XOR'ed into the hash signature
depending on which square is the ep square.

It is intersting that Bruce made a comment about this a while back.  He noted
that the same opening position reached by a different order of moves will
produce a different hash signature doing ep squares in this way.  Therefore it
does create a degree of inefficiency because (except for the ep move) the rest
of the position may have already been evaluated and in the hash table.


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