Author: Uri Blass
Date: 15:04:37 07/11/02
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On July 11, 2002 at 17:46:36, Omid David wrote: >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). >> >>Uri > >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). I agree that R=3 and R=4 should be also considered. From my experience in GCP test suites at 5 minutes per move recursive R=3 got the best results so far in GCP test suites(I do not know about games because I did not test it for games at slow time control but I suspect that it is possible that for movei R=3 may be even better than R=2 at the same time control). Note that the alternatives are not only R=2 and R=3 I suspect that starting with a small R in the first iterations may be even better. You can increase R during the search. There is no reason to do changes that do programs weaker at blitz on slow hardware. Uri
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