My understanding is that on a multi-core machine, mpi communication routines (MPI_SEND, etc) are implemented as memory copy instructions. Accordingly, message passing within a multi-core node should be very fast compared to your present cluster.
That said, It seems like all the performance benchmarks suggest that dual-core chips have the performances of 1.5-1.7 single core chips, so for the same number of nodes (defined as a CPU core) you wouldn't see the same output. All of this course depends on the structure of the code, memory usage, etc - these are just scaling estimates on my part. regards, Nathan On 10/2/07, Kwan Wing Keung <[EMAIL PROTECTED]> wrote: > > > This is perhap a naive question. > > 10 years before we started using the SP2, but we later changed to Intel > based linux beowulf in 2001. In our University there are quite a no. of > mpi-based parallel programs running in a 178 node dual-Xeon PC cluster > that was installed 4 years ago. > > We are now planning to upgrade our cluster in the coming year. Very > likely blade servers with multi-core CPUs will be used. To port these > mpi-based parallel programs to a multi-core CPU environment, someone > suggested that OpenMP should be used, such that the programs can be > converted to a multi-thread version. Nevertheless it may take time, and > the users may be reluctant to do so. Also for some of the installed > programs, we don't have the source code. > > Another user suggested that we may change slightly on the .machinefile > before executing the "mpirun" command. > > Suppose we are going to run a 8 mpi-task program on a quad-core cluster, > then only 2 CPUs should be selected, with the ".machinefile" looks like > "cpu0 cpu1 cpu0 cpu1 cpu0 cpu1 cpu0 cpu1" created, i.e. 4 mpi-tasks will > be spooled to CPU0 and 4 mpi-tasks will be spooled to CPU1. But the REAL > question will be: > Will EACH mpi-task be executed on ONE single core? > If not, then could there be any Linux utility program to help? > > I asked this question to one of the potential vendor, and the sales > suddenly suggested "Well, you can buy VMWARE to create virtual CPUs to do > so." Do you think it is logical? > > Thanks in advance. > > W.K. Kwan > Computer Centre > University of Hongkong > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > -- - - - - - - - - - - - - - - - - - - - - - Nathan Moore Assistant Professor, Physics Winona State University AIM: nmoorewsu - - - - - - - - - - - - - - - - - - - - -
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