Hello, ---------------------------------------------------- > >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? > Generally, each mpi-task should be executed on a single core, and if not, you can run 4 mpid on a single node. >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? > It was just a kidding. I suggest to use openmp on a single node and mpi among nodes for performance issues. And you may need to find a good mpi for your purpose. Regards, Li, Bo
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