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Subject: interference between verified null move R=3 and transposition table

Author: Stuart Cracraft

Date: 08:30:19 06/30/04


Hi -- I threw together a quick chess program in the past 3
weeks to do some research and recently added a testsuite
capability to at least get some measure of QA for changes.

I then ran testsuite on the program at about 12-13 seconds
per move against Win-at-Chess (300 positions) on a slow
(for these days) PC (1ghz P3 w/ 512mb).

To my surprise, Verified Null Move with R=3 scored better
without transposition table than with. Transposition table was
set to 0.5M entries in all cases.

See below where #3 result is greater than all the others.
It's puzzling to me why transposition table should reduce
the result for #3 down to the level of #5.

Has anyone else seen this with their program or programs
in general? It is most puzzling/counter-intuitive to me.

1. ***** base/plain/no nullmove/no transposition/no optimizations *****
*** Test score: 61% correct (183 out of 300)
*** Grand total nodes: 440075104 time: 3868.21
*** Average nodes/time/nps per test position: 1466917 13 113767

2. ****** opt trans *******
*** Test score: 67% correct (203 out of 300)
*** Grand total nodes: 620892160 time: 3635.11
*** Average nodes/time/nps per test position: 2069640 12 170804

3. ****** opt verified null 3 *******
*** Test score: 69% correct (207 out of 300)
*** Grand total nodes: 656987264 time: 3591.53
*** Average nodes/time/nps per test position: 2189958 12 182927

4. ****** opt trans verified null 2 *******
*** Test score: 64% correct (194 out of 300)
*** Grand total nodes: 663116096 time: 3521.66
*** Average nodes/time/nps per test position: 2210387 12 188296

5. ****** opt trans verified null 3 *******
*** Test score: 66% correct (200 out of 300)
*** Grand total nodes: 678707776 time: 3521.42
*** Average nodes/time/nps per test position: 2262359 12 192737

(I also tested against non-verified null move and its result was
far worse than the above which made sense, but that transposition
effect sent me for a loop.)

Any comments would be appreciated?

Stuart



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