[mpiwg-tools] PMPI and sessions init

[Martin Schulz]

Hi Joachim, all,

Yes, I think you are right - we probably didn't think this all the way through on the TelCon: as long as all items are loaded, the interceptions with PMPI should work, no matter when and where MPI calls are made. The only issue would be the load order of a tool vs. a library using MPI_Sessions, which could lead to situations where a tool wouldn't be able to catch the init calls.

Martin

PS: what do you mean with the environment variable in this scenario?



-- 
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
 
 

On 05.11.20, 19:00, "mpiwg-tools on behalf of Joachim Protze via mpiwg-tools" <mpiwg-tools-bounces at lists.mpi-forum.org on behalf of mpiwg-tools at lists.mpi-forum.org> wrote:

    Hi all,

    if I understood the discussion about MPI_Session_init and PMPI right, I
    don't think there exists an issue.
    By ld-preloading the PMPI tool, the tool can also intercept a call to
    MPI_Session_init, which might come from a library constructor before
    main. Even a function called from the library constructor of a static
    library can be intercepted by a ld-preloaded tool.

    For libraries, which are explicitly loaded by the MPI runtime during
    initialization, this would also work. For others, it depends on the
    ordering of calling the library constructor (might work by chance :).

    This was one of my main motivation of having such an environmental
    variable.

    Best
    Joachim


    -- 
    Dipl.-Inf. Joachim Protze

    IT Center
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