aidaros.dev_at_[hidden] wrote:
> Dear All
> I have a simple question.
> I got confused about when we should use MPI.
> MPI use in clusters, means there is no shared memory. Processors need to
> communicate other processors in different node by send/recieve
> mpi-functions.
> In Semmetric multiprocessor (SMP) computer, no cluster, it is shared
> memory,
> since it is shared memory (Single address space), processors need NOT to
> communicate with other processors by send/receive mpi-function. So what is
> the advantages using MPI on SMP?
I think your personal wording of the distinction between MPI
communication in shared memory and between nodes is confusing. It is
quite common for an optimized MPI application to out-perform an
equivalent OpenMP version, when running on an SMP platform. In such
cases, the development effort for the MPI version is likely to be larger.
A lot would depend on how easy it is to optimize the two versions you
are comparing.
For lam-mpi, the default scheme for message passing on little-endian
platforms involves a slow method for byte-reversing the messages.
Shared memory communication can be speeded up greatly with one of the
options, but lam is often judged by its defaults.
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