Thanks, for a quickly reply. I have four nodes (GigaEthernet), each node with two Quad Core E5410 at 2.33GHz, Mem 16Gb - DDR2 667Mhz., and definitely I'm not have the enough memory bandwidth for a reasonable speedup.
This may be a dummy question but in the second bullet says "its own memory bandwith of roughly 2 or more gigabytes", this means gigabytes/seconds, or refers to amount of memory per core?. Thanks a lot. Pedro 2010/4/14 Barry Smith <bsmith at mcs.anl.gov> > > Second bullet at > http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#computers > > Barry > > > On Apr 14, 2010, at 4:10 PM, Jed Brown wrote: > > On Wed, 14 Apr 2010 18:02:11 -0300, Pedro Torres < >> torres.pedrozpk at gmail.com> wrote: >> >>> Hello, >>> >>> Sorry if this questions its not appropiate for the petsc-list, but I >>> really >>> want to known what happen when I'm getting differente KSP time results. >>> For >>> example, allocating two process in the same node I get 6.24 sec, and when >>> allocating two process in two nodes (1 process per node) I get 4.7sec. >>> Is >>> there a memory contention problem in my node?? The problem get worst when >>> increase the number of process. >>> >> >> Sparse matrix kernels are primarily limited by memory bandwidth which >> does not increase much with multicore hardware (vendors rarely mention >> this). When you use multiple cores per socket, they have to share the >> available bandwidth, so you get lower performance. It's *usually* still >> faster to use the available cores, but the per-core performance is >> definitely lower than when using only one core per socket. >> >> Jed >> > > -- Pedro Torres GESAR/UERJ Rua Fonseca Teles 121, S?o Crist?v?o Rio de Janeiro - Brasil -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20100414/46b52aff/attachment.htm>
