Computer Chess Club Archives




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

Author: Robert Hyatt

Date: 13:53:45 02/28/00

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On February 28, 2000 at 16:20:21, Tom Kerrigan wrote:

>On February 28, 2000 at 13:51:25, Robert Hyatt wrote:
>>Who isn't including EP status in the hash signature?  I can't imagine _anyone_
>>not doing this.  It leads to simple failures that are easy to predict.
>I'm not sure the authors would appreciate it if I started talking about their
>algorithms in an open forum like this. I'm sure you understand.
>As for knowingly adding bugs--well, duh. I don't expect you to keep the damn
>"bug" IN. And you yourself said it would be easy to prove your point. So do it.

How about if I tell you that if you compute x=a/b where b=0 you are going
to have problems?  Do you need confirmation of the problem?  Or if you are
going to compute x=sqrt(b) where b is negative and you don't have a function
that understands complex (imaginary) numbers?

IE it seems intuitively obvious to the casual observer that if you don't
notice the difference between two positions where EP is possible in one, and
not in another, you will make mistakes.  EP is very common in my search
trees, based on simple 'counting' in a profiler to see how often such captures
are generated/made.  Way too often to ignore.  A hash signature collision is so
infrequent we get away with ignoring them. This is not that infrequent.

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