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

Author: Robert Hyatt

Date: 05:49:06 02/28/00

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On February 28, 2000 at 03:25:09, Tom Kerrigan wrote:

>On February 27, 2000 at 18:00:32, Robert Hyatt wrote:
>
>>I don't believe this can be safely overlooked, because the wrong repetition
>>value is a tiny part of a much bigger problem, that of not correctly hashing
>>positions...  the former may not happen often.  The latter happens thousands
>>of times every search.  Often enough that it will _definitely_ affect the
>>root score enough to make a difference.
>
>I would like to see some numbers to back up your argument.
>
>-Tom


3, 47.5, 2.71828, 3.14159265358979323846264, and -.2

All you have to do is run with and without EP hashed into your signature to
see the problem.  I lost a game early in the crafty development due to this.
Fortunately the IM in question sent me a message on ICC.  I searched a position
where an EP capture wasn't possible and found a forced mate.  I then searched
a position (identical except that an ep capture _was_ possible and announced a
mate.  He re-captured EP and mated me instead..  EP is a very common move in
the opening and early middlegame.



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