Determines the size of the group associated with a communictor
int MPI_Comm_size ( MPI_Comm comm, int *size )
- communicator (handle)
- number of processes in the group of comm (integer)
MPI_COMM_NULL is not considered a valid argument to this function.
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
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER
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_Errhandler_set; 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
- No error; MPI routine completed successfully.
- Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank).
- Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK).