Hi Howard,

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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.

I think the problem also appears if the original MPI_Init_thread uses FUNNELED. We probably need to add something there as well.

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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.

That kind of makes sense - but what happens if the second Session_Init is then on another thread? The funneled refers to a different thread.

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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.

Hmm, I understand the motivation and implementation implications, but this would kill the isolation then, which is also not good. Also, if two libraries have separate sessions, it is often not even possible to avoid this. Almost seems like we should deprecate funneled and serialized. Another item to cover next Monday __. Martin Howard On 2/13/21, 2:53 PM, "mpiwg-sessions on behalf of Martin Schulz via mpiwg-sessions" <[email protected] on behalf of [email protected]> 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? Thanks, Martin -- 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: [email protected] _______________________________________________ mpiwg-sessions mailing list [email protected] https://lists.mpi-forum.org/mailman/listinfo/mpiwg-sessions