17.2.194. MPI_Group_size

MPI_Group_size - Returns the size of a group.

17.2.194.1. SYNTAX

17.2.194.1.1. C Syntax

#include <mpi.h>

int MPI_Group_size(MPI_Group group, int *size)

17.2.194.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_GROUP_SIZE(GROUP, SIZE, IERROR)
     INTEGER GROUP, SIZE, IERROR

17.2.194.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Group_size(group, size, ierror)
     TYPE(MPI_Group), INTENT(IN) :: group
     INTEGER, INTENT(OUT) :: size
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.194.2. INPUT PARAMETERS

  • group: Group (handle).

17.2.194.3. OUTPUT PARAMETERS

  • size: Number of processes in the group (integer).

  • IERROR: Fortran only: Error status (integer).

17.2.194.4. DESCRIPTION

MPI_Group_size returns in size the number of processes in the group. Thus, if group = MPI_GROUP_EMPTY, then the call will return size = 0. On the other hand, a call with group = MPI_GROUP_NULL is erroneous.

17.2.194.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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.