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Subject: Re: Capture/recapture extensions

Author: Will Singleton

Date: 08:48:33 12/14/98

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On December 14, 1998 at 05:34:41, Andrew Williams wrote:

>Hello all,
>
>I'm trying to work out how to implement capture/recapture extensions in
>my program. I have had a look at crafty and gnuchess and I've tried
>several approaches, viz:
>
>1 Extend when a capture followed by recapture restores the material
>  balance we had at the root.
>
>2 Extend when the capture/recapture restores the material balance from
>  before the sequence.
>
>3 Extend when the capture and recapture are on the same square (and same
>  material value).
>
>In all these cases, I seem to get a much larger tree and often lose a ply
>of search because of this. So, three questions:
>
>(a) Am I on the right lines with 1, 2 and 3 above?
>(b) Is it normal to lose depth when doing this?
>(c) Generally speaking, it better to complete d7 with this extension than
>    d8 without it?
>
>I realize that these questions probably aren't yes/no style questions, so
>thanks to anyone who takes the trouble to reply.
>
>Regards
>
>Andrew Williams
>(Author of PostModernist on ICC)


Hi Andrew,

I current use (1), and generate a few extra nodes, but not an extra ply's worth.
 I find I get better ordering with the capture extension in.

I'll have to take a look at the code, but I think I have some restriction on
recaptures that limits the tree growth.  But generally speaking, the recapture
extension is almost universally used, and has been shown effective in several
studies.

Will




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