[mpiwg-sessions] [EXTERNAL] Question on MPI_THREAD_FUNNELED

Pritchard Jr., Howard howardp at lanl.gov
Mon Feb 15 11:46:32 CST 2021

Hi Martin,

I recall we decided to leave the behavior of thread support level when using multiple sessions/world model up to the implementation.   However, in the case of MPI_THREAD_FUNNELED we should probably add a blurb about not doing this in the advice to users in the Session Creation and Destruction Methods.

My first guess based on the openmpi prototype is that if one session is initialized with funneled, then all subsequent created sessions or mpi init thread will be supported at funnel level.  

For your thread serialized question I would say the answer is no, unless under the covers the implementation is always working in effectively thread multiple mode.


On 2/13/21, 2:53 PM, "mpiwg-sessions on behalf of Martin Schulz via mpiwg-sessions" <mpiwg-sessions-bounces at lists.mpi-forum.org on behalf of mpiwg-sessions at lists.mpi-forum.org> wrote:

    Hi all,

    Can MPI_Session_Init be called with requesting MPI_THREAD_FUNNELED from two different threads? If so, does MPI return MPI_THREAD_FUNNELED or MPI_THREAD_SERIALIZED? Can I match this with MPI_Init_thread using  MPI_THREAD_FUNNELED  from a different thread?

    If we assume full isolation, that should work, right?

    Also, can I make two concurrent MPI calls from two different threads at the same time, assuming the MPI calls use MPI objects derived from two different sessions, both initialized with MPI_THREAD_SERIALIZED?



    Prof. Dr. Martin Schulz, Chair of Computer Architecture and Parallel Systems
    Department of Informatics, TU-Munich, Boltzmannstraße 3, D-85748 Garching
    Member of the Board of Directors at the Leibniz Supercomputing Centre (LRZ)
    Email: schulzm at in.tum.de

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