DragonFly On-Line Manual Pages
MPI_Query_thread(3) MPI MPI_Query_thread(3)
MPI_Query_thread - Return the level of thread support provided by the
int MPI_Query_thread( int *provided )
- 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
- 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
- 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
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
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
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.