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Subject: Re: Recapture Extension

Author: Georg v. Zimmermann

Date: 03:09:01 01/10/02

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On January 09, 2002 at 10:15:53, David Rasmussen wrote:

>Some time ago we talked about the recapture extension. Bob's experiments with
>Crafty seemed to show that recapture extension was a bad idea at least for his
>program.
>
>How many people have the recapture extension because they positively believe
>that it is better for their program, and how many has removed it from their
>program because the positively believe that it is bad for their program?
>
>I am sure a lot of people have it or don't have it, but for no specific reason,
>that is, they have not tested the effect of this extension thoroughly.
>
>/David

I do this:


  /* Capture extensions.
   * Conditions:
   * Last move was a capture of the piece that
   * just moved and it was the only way to capture it
   */

	if ((!wasNullMove) && (AIBoard.captureExtensionCondition()))

		{
			extensions += CAPTURE_EXTENSION;
                        stats_capext+= CAPTURE_EXTENSION;

			#ifdef GAMETREE
			if (tree_positionsSaved < GAMETREE)
			{ fprintf(fi[ply],"Capture extension: depth+ %d<br>\n", CAPTURE_EXTENSION); }
			#endif
		}


It works very well for me. When I implemented this idea in Crafty instead of its
original recap extensions Crafty solved one position more in WAC 5secs on my
k6ii/800. I didnt play enough games to statistically prove it got better,I think
the improvement was small but existing.

Georg



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