On Thu, 2009-04-30 at 07:18 -0700, Ihsan Erikat wrote: please check out previous lengthy discussions on the subject in the mailing list archives _again_. this topic has been discussed repeatedly and people have done benchmarks to demonstrate and understand how the various parallelization options help under specific environments. particularly the number of cpus per node, cores per cpu, main memory per cpu/core, cache memory per cpu/core in combination with the interconnect (tcp/ip, infiniband/myrinet/...) can lead to different results. in some cases it may even better to not use all cpu cores in order maximize cache usage, in others it may be important to use the more communication demanding parallelization scheme to reduce the per process memory use. ... and this is only the beginning. compiler vendor and flags as well as BLAS/LAPACK and communication libraries can have and impact, not to mention the setup and configuration of machines. (e.g. modern linux distributions come with SELinux enabled which effectively trashes the cache by randomizing the stack frame location and lots of useless auto-configuration demons running that interrupt the kernel needlessly and thus create a lot of OS jitter which affects latency sensitive applications. running a "lean mean computing machine" requires some effort on many levels...).
in short: do tests and figure it out yourself. what works best depends very much on your input set size, network, hard- and software. cheers, axel. > Hello all > I am running pwscf on 10 CPU and the k points in my file is 3x6x1. > > When I use the command mpirun -np xx pw.x -npool x , how can I > choose the effective number of processors and pools . I read the > manual and the forum archive, but I don`t know how to choose these > numbers. I`ll appreciate any help. > > > > best regards > Ihsan Erikat > Physics department-Jordan University > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- ======================================================================= Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu http://www.cmm.upenn.edu Center for Molecular Modeling -- University of Pennsylvania Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323 tel: 1-215-898-1582, fax: 1-215-573-6233, office-tel: 1-215-898-5425 ======================================================================= If you make something idiot-proof, the universe creates a better idiot.
