Author: Vincent Diepeveen
Date: 01:38:00 05/07/04
Go up one level in this thread
On May 06, 2004 at 19:03:48, martin fierz wrote: >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... Bob has tested the SMP version 1 cpu versus SMP version 2 or 4 cpus. The single cpu version of crafty is just hardly existing because of a stupid thread pointer which is a constant. Optimizing that crafty is 5% faster for sure in time single cpu at opteron. He should test the single cpu version versus the SMP version IMHO. Even then speedup will be much better than the 2.8 from the quad xeon, the opteron is a real highend chip which is ideal for SMP applications depending completely upon cache and memory subsystems, unlike the intel xeon. In future speedups will again get better. In 2005 or 2006 the opteron will be released as a dual core chip. So you have on chip CMP then. >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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