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check extensions.
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Robert Hyatt



Joined: 27 Feb 2006
Posts: 20311
Location: Birmingham, AL

PostPost subject: check extensions.    Posted: Tue Oct 28, 2008 1:56 pm Reply to topic Reply with quote

I ran a few tests last night since I had recently seen a discussion about check extensions, and found some interesting results. First the data:

Code:

Crafty-22.2R26-2  2587    5    5
Crafty-22.2R26-3  2599    4    4
Crafty-22.2R26-4  2608    5    5
Crafty-22.2R26-5  2579    4    4

Crafty-22.2R29-0  2597    5    5
Crafty-22.2R29-1  2597    5    5
Crafty-22.2R29-2  2598    4    4
Crafty-22.2R29-3  2597    5    5

Crafty-22.2R30-0  2597    5    5
Crafty-22.2R30-1  2594    5    5
Crafty-22.2R30-2  2598    4    4
Crafty-22.2R30-3  2597    5    5


OK, what are these? Crafty-22.2R26, R29 and R30 are identical versions of Crafty, except R26 varies the in-check extension from 1 (1/4 ply) to 5 (5/4 ply). R29 varies the one-legal-reply-to-check extension from 1/4 ply to 3/4 ply (default), R30 varies the mate-threat extension from 1/4 ply to 3/4 ply. In Crafty, the defaults are 4 (1 ply) for in-check, and 3 (3/4 ply) for the other two. Each of the above test versions played 32,000 games.

The rather surprising results were that the one-legal-reply and mate threat extensions appear to be completely useless, and I am going to remove them completely. The in check extension is more valuable, and surprisingly 1.0 plies seems to be the optimal value...

I had already discovered that the passed pawn push extension was no good, ditto for the recapture extension. It appears that the only one that is actually useful is the give-check or in-check (in Crafty it is actually a give-check extension where I extend when I give check rather than extending at the next ply when I escape check).
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Display posts from previous:   
Subject Author Date/Time
check extensions. Robert Hyatt Tue Oct 28, 2008 1:56 pm
      Re: check extensions. Tord Romstad Tue Oct 28, 2008 2:59 pm
            Re: check extensions. Robert Hyatt Tue Oct 28, 2008 3:26 pm
      Re: check extensions. H.G.Muller Tue Oct 28, 2008 3:26 pm
            Re: check extensions. Robert Hyatt Tue Oct 28, 2008 6:42 pm
                  Re: check extensions. Sam Hamilton Tue Oct 28, 2008 7:22 pm
                        Re: check extensions. Robert Hyatt Tue Oct 28, 2008 7:46 pm
                              Re: check extensions. Sam Hamilton Tue Oct 28, 2008 8:00 pm
      Re: check extensions. Jarkko Tue Oct 28, 2008 9:13 pm
            Re: check extensions. Robert Hyatt Tue Oct 28, 2008 9:44 pm
                  Re: check extensions. Edsel Apostol Wed Oct 29, 2008 1:56 am
                        Re: check extensions. Sam Hamilton Wed Oct 29, 2008 2:21 am
                              Re: check extensions. Edsel Apostol Wed Oct 29, 2008 2:30 am
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