[starpu-devel] [StarPU-MPI: no dedicated thread for communication; function to set MPI_THREAD_MULTIPLE]

[Maxim Abalenkov <maxim.abalenkov@gmail.com>]

Dear all,

How are you? I hope all is well with you. I have two relatively simple questions on StarPU-MPI:

1) I would like StarPU-MPI to use all available threads for computation (i.e. avoid to have a dedicated thread for MPI communication). To achieve that I create a StarPU configuration structure and set the variable ‘reserve_ncpu = 0’.

    // ensure StarPU does not reserse CPUs solely for MPI communication

    struct starpu_conf conf = {.reserve_ncpus = 0};

    int status = starpu_conf_init(&conf);

    STARPU_CHECK_RETURN_VALUE(status, "starpu_conf_init");

    // initialise StarPU MPI

    status = starpu_mpi_init_conf(&argc, &argv, 1, MPI_COMM_WORLD, &conf);

    STARPU_CHECK_RETURN_VALUE(status, "starpu_mpi_init_conf");

    starpu_mpi_comm_rank(MPI_COMM_WORLD, &rank);

    starpu_mpi_comm_size(MPI_COMM_WORLD, &np);

However, when I print out timing results for each CPU worker I see only seven workers:

Worker CPU 0…

…

Worker CPU 6…

Am I creating the StarPU configuration incorrectly or is this (the hardware) reality of the Apple M2 CPU?

2) Many StarPU-MPI examples use MPI_THREAD_MULTIPLE to allow multiple simultaneous calls to MPI library. In the examples, the value is set by calling ‘MPI_Init_thread()’. As I understand it is defined in various ‘helper.h’ files in the ‘tests’ directory. Is there a convenient StarPU API function to set ‘MPI_THREAD_MULTIPLE'? I tried including these helper header files. But I immediately face the errors of being unable to find “common/config.h”.

Thank you for your help and have a great day ahead!

—

Best wishes,

Maxim

Maxim Abalenkov \\ maxim.abalenkov@gmail.com
+44 7 486 486 505 \\ www.maxim.abalenkov.uk