17.2.184. MPI_Group_compare

MPI_Group_compare — Compares two groups.

17.2.184.1. SYNTAX

17.2.184.1.1. C Syntax

#include <mpi.h>

int MPI_Group_compare(MPI_Group group1, MPI_Group group2,
    int *result)

17.2.184.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_GROUP_COMPARE(GROUP1, GROUP2, RESULT, IERROR)
    INTEGER GROUP1, GROUP2, RESULT, IERROR

17.2.184.1.3. Fortran 2008 Syntax

USE mpi_f08

MPI_Group_compare(group1, group2, result, ierror)
    TYPE(MPI_Group), INTENT(IN) :: group1, group2
    INTEGER, INTENT(OUT) :: result
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.184.2. INPUT PARAMETERS

• group1 : First group (handle).

• group2 : Second group (handle).

17.2.184.3. OUTPUT PARAMETERS

• resultInteger which is MPI_IDENT if the order and members of

  the two groups are the same, MPI_SIMILAR if only the members are the same, and MPI_UNEQUAL otherwise.

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

17.2.184.4. DESCRIPTION

MPI_IDENT results if the group members and group order is exactly the same in both groups. This happens for instance if group1 and group2 are the same handle. MPI_SIMILAR results if the group members are the same but the order is different. MPI_UNEQUAL results otherwise.

17.2.184.5. ERRORS

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

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

• MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

• MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.

• MPI_ERRORS_RETURN Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

• MPI_File_create_errhandler then MPI_File_set_errhandler

• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

• MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.