NAME

       MPI_Group_size - Returns the size of a group.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Group_size(MPI_Group group, int *size)

Fortran Syntax

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

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

C++ Syntax

       #include <mpi.h>
       int Group::Get_size() const

INPUT PARAMETERS

       group     Group (handle).

OUTPUT PARAMETERS

       size      Number of processes in the group (integer).

       IERROR    Fortran only: Error status (integer).

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.

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.

4.1.6                                             Sep 30, 2023                                 MPI_Group_size(3)