A side comment about the Stream benchmark: it is HIGHLY sensitive to placement and length of the arrays in memory. Different compilers can place the arrays differently in memory, which can result in very different results. This can happen with different compilers, different switches on the same compiler, or even different versions of the same compiler.
So, when you run the Stream test for comparison purposes, make sure you compile once, measure twice. :-) Mike Fintan Ryan wrote: > Hi, > >> On 7/31/07, Lars Tunkrans <[EMAIL PROTECTED]> wrote: >> >>> So yes , Thanks to the Stream Benchmark I have now sort of proved >>> that the new >>> DDR2 memory controller on the AM2 socket Athlon's very nearly >>> doubles memory throughput. >>> >> BTW, if you are really into getting the best possible Stream number >> for your machines, try some extra flags like: -m64 -xopenmp >> >> * -xopenmp will use both cores of your X2s, so it may be interesting >> to see the results... :) >> >> > > Setting OMP_NUM_THREADS to physical processor and core count and > comparing results after compiling with -xopenmp is generally an > interesting metric to look at as well (the default behaviour is to rely > on *OMP_DYNAMIC*, but I'm not sure how that evaluates cores v's threads). > >> Also, large page and -xprefetch may help, but you will end up spending >> lots of time to get an extra few % >> >> > I found -xprefetch -xprefetch_level=3 made the most difference the last > time I looked, but as Rayson stated its a lot of experimentation for a > small difference. > > - Fintan > >> Rayson >> >> >> >>> Thanks again >>> >>> //Lars >>> >>> >>> This message posted from opensolaris.org >>> _______________________________________________ >>> perf-discuss mailing list >>> perf-discuss@opensolaris.org >>> >>> >> http://gridengine.sunsource.net/ >> _______________________________________________ >> perf-discuss mailing list >> perf-discuss@opensolaris.org >> > > _______________________________________________ > perf-discuss mailing list > perf-discuss@opensolaris.org _______________________________________________ perf-discuss mailing list perf-discuss@opensolaris.org
