On Sat, May 16, 2009 at 2:34 PM, Tiago Marques <a28...@ua.pt> wrote: > One of the codes, VASP, is very bandwidth limited and loves to run in a > number of cores multiple of 3. The 5400s are also very bandwith - memory and > FSB - limited which causes that they sometimes don't scale well above 6 > cores. They are very fast per core, as someone mentioned, when compared to > AMD cores.
Thanks Tiago. This is super useful info. VASP is one of our major "users" too. Possibly 40% of the cpu-time. Rest is a similar computational chemistry code, DACAPO. It would be interesting to compare my test-run times on our AMD-Opterons (Barcelona). Is is possible to share what your benchmark job was? Since you mention VASP is bandwidth limited do you mean memory bandwidth or the interconnect? Maybe this question itself is naiive. Not sure. What interconnect do you use? We have gigabit ethernet dual bonded. A side note: I wasn't aware of VASP preferring multiples of 3 cpus. I'm not a big VASP user myself but I see my users often submit jobs on multiples of 8 since we have 8 cpus / box. Is that a big drag on performance? Why? I thought VASP parallelized over bands so could scale well to any cpu-multiple? -- Rahul _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
