Author: Robert Hyatt
Date: 08:19:53 05/07/04
Go up one level in this thread
On May 07, 2004 at 04:38:00, Vincent Diepeveen wrote: >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. There is _very_ little difference. And such testing would require a _major_ rewrite. Pointless. > >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. Funny guy, knowing that I have been getting these _same_ speedup numbers on my dual and quad xeon boxes. Also knowing that you keep claiming that Crafty sucks on a NUMA box. Why don't you pick an argument and stick with it??? > >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. That has _nothing_ to do with parallel speedup. > >>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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