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

Author: Omid David

Date: 13:38:50 07/11/02


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). 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.

So, apparently R=2 is not _by_far_ better than R=3 as some assume. I believe
Bruce Moreland had also some good results with R=3 that show it's not too
inferior to R=2. Has anyone conducted similar experiments?



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