Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder2.hal-mli.net!feeder.erje.net!eu.feeder.erje.net!news2.arglkargh.de!news.swapon.de!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: blmblm@myrealbox.com Newsgroups: comp.parallel.mpi Subject: Re: Basic question about MPI Date: 2 Feb 2013 19:13:28 GMT Organization: None Lines: 29 Message-ID: References: <31beb7a0-0dd0-4647-8c63-12a67b9c0f6a@googlegroups.com> X-Trace: individual.net UDQRoaV9EBaXjN8MVJY01QfYZ2+MHOR6ELo53hxTd80JlPuQ4NJPUn1BMmCTjsXzNb X-Orig-Path: not-for-mail Cancel-Lock: sha1:yddaXXYfAwLzIJxwVIkEEdT/yjw= X-Newsreader: trn 4.0-test76 (Apr 2, 2001) Xref: csiph.com comp.parallel.mpi:52 In article <31beb7a0-0dd0-4647-8c63-12a67b9c0f6a@googlegroups.com>, wrote: > > Hello, > > I have a very basic question about MPI. > > I have a computer with 8 processors (each with 8 cores). What is the difference between if I run a program simply by "./program" and "mpirun -np 6 /path/to/program" ? In the first case does the program just use one processor of the 8? If I want the program to use all the 8 processors at the same time, then I have to do with mpirun? "./program" just runs the program (i.e., creates one process). "mpirun -np 6 ...." starts six copies of the program (i.e., creates six processes). As best I know this is the normal way of starting an MPI program meant to run on multiple processors. > > Something fundamental is buggin me. Any explanations will be highly appreciated. > So I hope you're still checking the group .... > Thank you, > Pradeep > -- B. L. Massingill ObDisclaimer: I don't speak for my employers; they return the favor.