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Subject: Re: Surprising results from Chess experiment

Author: Peter McKenzie

Date: 22:50:42 07/11/99

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On July 11, 1999 at 16:19:24, Pat King wrote:

>I recently ran a series of tests on SweetReason 1.7, my chess program, turning
>on and off various features to determine their effect on search speed and
>program strength. In general, I got expected results. Ie, my program appears to
>gain 140 Elo points/ply, and the typically reported figure's about 200 (effect
>of increased knowledge in evaluation?). The surprise came in evaluating the
>check extension. Common sense would lead one (well, me) to expect the check
>extension to increase strength and decrease speed. I had exactly the opposite
>effect -- using check extension appears to drop 200 Elo points, but also reduce

Yes, this is surprising!  I have heard some people say bad things about check
extensions though.  I haven't done any good experiments with them lately,
something else for the todo list...
Are you sure you didn't have a bug?

>the nodes visited in a fixed depth search by 40%! I can write off the Elo effect
>to small sample size, but the other figure has enough data behind it to stand
>up. Could the improved evaluation of "checky" positions cause enough cutoffs to
>do this?

what was your exact methodology?

I assume you ran a bunch of test positions to a fixed depth?  If so, which
positions?  What depth?  I would be interested in trying to reproduce this
result.

peter



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