Author: martin fierz
Date: 16:03:48 05/06/04
aloha! bob posted some crafty logfiles running a 24-position test set on his ftp site (for anyone else crazy enough to repeat what i did: ftp.cis.uab.edu/pub/hyatt/smpdata) these are logfiles of crafty running as single CPU, dual, or quad; on opterons. i took the last completed ply on the single CPU set for each position (marked by -> in the logfile, i hope...), wrote down the time to complete this ply, and did this for all logfiles. there are 9 of these, 4 repeats for 2 and 4 CPUs. i computed the speedup for time-to-finish-ply-X for each of the multi-CPU runs with the following results: 2 CPUs: 1.961 +- 0.093 1.888 +- 0.074 1.846 +- 0.078 1.763 +- 0.084 4 CPUs: 3.15 +- 0.15 3.29 +- 0.20 3.06 +- 0.12 3.19 +- 0.13 now, is there any meaning to this, and if yes, what? point #1 to make is that the numbers here are mutually consistent with each other, given the error margins quoted. which should show those skeptical of this statistical approach that it makes sense to do it this way, rather than to just write "i measured speedup 3.1". point #2 is that the speedup on 4 CPUs on average is 3.17 in this test, which might be one point for bob in the duel with vincent; although i suspect that the speedup depends on the hardware architecture - i will leave this question to the parallel computing experts though... point #3 is perhaps most important for the bob vs vincent duel: the standard error for a 4 CPU test run is on the order of 0.2. if vincent's tests were with a similarly small number of positions, then the differences measured in these experiments (2.8 / 3.0 / 3.1) are statistically insignificant, and the whole argument is pointless :-) cheers martin disclaimer: i computed the search time in seconds from crafty's log file by converting minutes:seconds to seconds in my head. i may have made a mistake here or there, although i did my best not to - but it's late at night and quite boring to look through crafty logfiles...
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