Return the level of thread support provided by the MPI library


int MPI_Query_thread( int *provided )

Output Parameters

Level of thread support provided. This is the same value that was returned in the provided argument in MPI_Init_thread.


The valid values for the level of thread support are:
Only one thread will execute.
The process may be multi-threaded, but only the main thread will make MPI calls (all MPI calls are funneled to the main thread).
The process may be multi-threaded, and multiple threads may make MPI calls, but only one at a time: MPI calls are not made concurrently from two distinct threads (all MPI calls are serialized).
Multiple threads may call MPI, with no restrictions.

If MPI_Init was called instead of MPI_Init_thread, the level of thread support is defined by the implementation. This routine allows you to find out the provided level. It is also useful for library routines that discover that MPI has already been initialized and wish to determine what level of thread support is available.

Thread and Interrupt Safety

This routine is both thread- and interrupt-safe. This means that this routine may safely be used by multiple threads and from within a signal handler.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.


All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

No error; MPI routine completed successfully.