[mvapich-discuss] regarding hybrid MPI/pthread and RDMA

[Krishna Kandalla]

Hi Sandeep,
        If you are not issuing MPI operations from inside the omp regions,
the thread-level should not matter. However, if the openmp threads are
calling MPI functions, you could request for MPI_THREAD_MULTIPLE  through
the MPI_Init_thread call. You do not have to use any config-time options to
enable the multi-threading support.
        Could you please let us know more about the MVAPICH2 version that
you are currently using?  We generally recommend users to disable CPU
affinity for the MPI + Openmp applications (
http://mvapich/support/user_guide_mvapich2-1.8rc1.html#x1-1040009.1.3).
However, if you could upgrade to our latest MVAPICH2 1.8rc1 release, we
have improved our CPU affinity support by introducing different binding
levels that are specifically geared towards hybrid cases (
http://mvapich/support/user_guide_mvapich2-1.8rc1.html#x1-530006.3.1).

> And lastly with respect to mvapich how do I go about performing RDMA style
> communication. Is it the MPI_Put and MPI_get set of collectives?

         MVAPICH2 already uses RDMA-based communication. Please let us know
if you have any other questions.

Thanks,
Krishna
(http://www.cse.ohio-state.edu/~kandalla)



On Mon, Mar 26, 2012 at 1:48 PM, Sandeep Gupta <gupta.sandeep at gmail.com>
wrote:
> Hi,
>  I am exploring hybrid MPI/pthread programming model and  had couple of
> questions/clarifications to ask for.  I wanted to know what options there
> exists with mvapich2 for programming in the hybrid model. Currently I am
> using MPI with  thread_support_multiple.
> My question is that do I have to check for support level
> THREAD_SUPPORT_MULTIPLE?. If the program does not have thread support
> multiple does that mean it won't work in hybrid mode irrespective of the
> mvapich version.
> My second question is that are there any alternative way of achieving the
> hybrid  computation model?.
> And lastly with respect to mvapich how do I go about performing RDMA style
> communication. Is it the MPI_Put and MPI_get set of collectives?
>
> Thanks for taking a look.
> Best,
> Sandeep
>
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