NAME¶

MPI_Query_thread - 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.

SEE ALSO¶

MPI_Init
MPI_Init_thread