Copyright 2006-2008 Sun Microsystems, Inc.
Copyright (c) 1996 Thinking Machines Corporation
Copyright (c) 2010-2015 Cisco Systems, Inc. All rights reserved.
$COPYRIGHT$
#include <mpi.h> int MPI_Init_thread(int *argc, char ***argv, int required, int *provided)
USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_INIT_THREAD(REQUIRED, PROVIDED, IERROR) INTEGER REQUIRED, PROVIDED, IERROR
USE mpi_f08 MPI_Init_thread(required, provided, ierror) INTEGER, INTENT(IN) :: required INTEGER, INTENT(OUT) :: provided INTEGER, OPTIONAL, INTENT(OUT) :: ierror
#include <mpi.h> int MPI::Init_thread(int& argc, char**& argv, int required) int MPI::Init_thread(int required)
1i argc C/C++ only: Pointer to the number of arguments.
1i argv C/C++ only: Argument vector.
1i required Desired level of thread support (integer). . .
1i provided Available level of thread support (integer).
1i IERROR Fortran only: Error status (integer). . .
2.4i MPI_THREAD_SINGLE Only one thread will execute.
2.4i MPI_THREAD_FUNNELED If the process is multithreaded, only the thread that called MPI_Init_thread will make MPI calls.
2.4i MPI_THREAD_SERIALIZED If the process is multithreaded, only one thread will make MPI library calls at one time.
2.4i MPI_THREAD_MULTIPLE If the process is multithreaded, multiple threads may call MPI at once with no restrictions. .
The level of thread support available to the program is set in provided, except in C++, where it is the return value of the function. In Open MPI, the value is dependent on how the library was configured and built. Note that there is no guarantee that provided will be greater than or equal to required. Also note that calling MPI_Init_thread with a required value of MPI_THREAD_SINGLE is equivalent to calling MPI_Init. All MPI programs must contain a call to MPI_Init or MPI_Init_thread. Open MPI accepts the C/C++ argc and argv arguments to main, but neither modifies, interprets, nor distributes them:
{ /* declare variables */ MPI_Init_thread(&argc, &argv, req, &prov); /* parse arguments */ /* main program */ MPI_Finalize(); }.
shell$ ompi_info | grep -i thread Thread support: posix (mpi: yes, progress: no) shell$.
The "mpi: yes" portion of the above output indicates that Open MPI was compiled with MPI_THREAD_MULTIPLE support. .
Note that MPI_THREAD_MULTIPLE support is only lightly tested. It likely does not work for thread-intensive applications. Also note that only the MPI point-to-point communication functions for the BTL's listed below are considered thread safe. Other support functions (e.g., MPI attributes) have not been certified as safe when simultaneously used by multiple threads. .
tcp sm mx elan self.
Note that Open MPI's thread support is in a fairly early stage; the above devices are likely to work , but the latency is likely to be fairly high. Specifically, efforts so far have concentrated on correctness , not performance (yet). . .
MPI_Init MPI_Initialized MPI_Finalize MPI_Finalized