man MPI_Query_thread (3): Returns the current level of thread support

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Query_thread(int *provided)

Fortran Syntax

INCLUDE 'mpif.h'
MPI_QUERY_THREAD(PROVIDED, IERROR)
        INTEGER PROVIDED, IERROR

C++ Syntax

#include <mpi.h>
int MPI::Query_thread()

OUTPUT PARAMETERS

provided: C/Fortran only: Level of thread support (integer).
IERROR: Fortran only: Error status (integer).

DESCRIPTION

This routine returns in provided the current level of thread support. If MPI was initialized by a call to MPI_Init_thread, provided will have the same value as was returned by that function.

The possible values of provided are as follows:

MPI_THREAD_SINGLE: Only one thread may execute.
MPI_THREAD_FUNNELED: If the process is multithreaded, only the thread that called MPI_Init[_thread] may make MPI calls.
MPI_THREAD_SERIALIZED: If the process is multithreaded, only one thread may make MPI library calls at one time.
MPI_THREAD_MULTIPLE: If the process is multithreaded, multiple threads may call MPI at once with no restrictions.

NOTES

In Open MPI, provided is always MPI_THREAD_SINGLE, unless the program has been linked with the multithreaded library, in which case provided is MPI_THREAD_MULTIPLE.

ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI::Exception object.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.