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Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Omid David

Date: 14:46:36 07/11/02

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On July 11, 2002 at 17:41:08, Uri Blass wrote:

>On July 11, 2002 at 16:38:50, Omid David wrote:
>>As part of an extensive research (will be published soon), we tested null-move
>>pruning with fixed depth reductions of R=2 and R=3 on about 800 positions of
>>"mate in 4" (searched to depth of 8 plies) and "mate in 5" (searched to depth of
>>10 plies). The results naturally show that R=2 has greater tactical performance
>>(greater number of checkmate detection).
>This is not the right test.
>It is clear that if you search to fix depth R=2 is going to be better.
>The question is what happens when you search for the same time.
> However, we also conducted about
>>hundred self-play matches under 60min/game time control between R=2 and R=3. The
>>outcome is a rather balanced result (R=2 only a little better). Considering that
>>the tests where conducted on a rather slow engine (100k nps), on faster engines
>>R=3 is expected to perform better.
>I think that a better test should include different programs and not the same
>program against itself.
>Another point is that R=2 and R=3 are not the only possibilities.
>>So, apparently R=2 is not _by_far_ better than R=3 as some assume.
>I suspect that it is dependent on the program(results may be different for
>programs with different qsearch and different evaluation).

I don't expect R=2 to gain more from greater speed than R=3. As a matter of fact
as Dr.Hyatt recently mentioned with faster hardware in the future, R=3 might
reach depths in which the total saving would be more significant than tactical
deficiency (deeper search would compensate for it). In such cases one might even
think of R=4 at some parts of the search tree (or as Dr.Hyatt just mentioned an
adaptive R=3~4 value).

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