Manpages - MPI_Group_size.3

MPI_Group_size - Returns the size of a group.

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

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

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

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

group

Group (handle).

size

Number of processes in the group (integer).

IERROR

Fortran only: Error status (integer).

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.

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.