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Subject: Re: When to stop searching captures?

Author: Amir Ban

Date: 17:10:49 09/15/98

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On September 15, 1998 at 18:51:00, John Coffey wrote:

>Let say hypothetically that I have a program that is doing a simple
>3 ply search, but will extend its look ahead for every capture.  The question
>becomes, how far should the look ahead be extended?  The last time I wrote
>a chess program (1987) I found that the program would examine frivilous
>captures out to infinity if I didn't put a limit on it.  (I literally had
>20 captures in a row.)
>
>So say I limit the extensions to 2*N, where if N is 3 then 2*N equals 6.
>Seems to me that this might not yield an accurate result and could still give
>lots of frivilous captures.
>
>John Coffey

The half-ply concept was originally introduced in Junior to deal with captures.
This was my first deviation from simple brute-force. I decided that a capture
will count as half a ply only. The rationale was that in a pair of captures,
there is usually only one free choice, so it should count as one ply, and the
number of plies become more or less the number of free choices (in a superficial
way).

I later applied this to other things, but captures are still handled this way,
so you can say that Junior supports your 2*N rule.

Amir




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