17.2.190. MPI_Group_incl — Open MPI 5.0.8 documentation

# 17.2.190. MPI_Group_incl

MPI_Group_incl — Produces a group by reordering an existing group and taking only listed members.

## 17.2.190.1. SYNTAX

### 17.2.190.1.1. C Syntax

    #include <mpi.h>

    int MPI_Group_incl(MPI_Group group, int n, const int ranks[],
        MPI_Group *newgroup)

### 17.2.190.1.2. Fortran Syntax

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

    MPI_GROUP_INCL(GROUP, N, RANKS, NEWGROUP, IERROR)
        INTEGER GROUP, N, RANKS(*), NEWGROUP, IERROR

### 17.2.190.1.3. Fortran 2008 Syntax

    USE mpi_f08

    MPI_Group_incl(group, n, ranks, newgroup, ierror)
        TYPE(MPI_Group), INTENT(IN) :: group
        INTEGER, INTENT(IN) :: n, ranks(n)
        TYPE(MPI_Group), INTENT(OUT) :: newgroup
        INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 17.2.190.2. INPUT PARAMETERS

- `group` : Group (handle).

- `n`Number of elements in array ranks (and size of

    newgroup)(integer).

- `ranks`Ranks of processes in group to appear in newgroup (array of

    integers).

## 17.2.190.3. OUTPUT PARAMETERS

- `newgroup`New group derived from above, in the order defined by

    ranks (handle).

- `ierror` : Fortran only: Error status (integer).

## 17.2.190.4. DESCRIPTION

The function MPI_Group_incl creates a group group_out that consists of the n processes in group with ranks rank[0], …, rank[n-1]; the process with rank i in group_out is the process with rank ranks[i] in group. Each of the n elements of ranks must be a valid rank in group and all elements must be distinct, or else the program is erroneous. If n = 0, then group_out is MPI_GROUP_EMPTY. This function can, for instance, be used to reorder the elements of a group.

## 17.2.190.5. NOTE

This implementation does not currently check to ensure that there are no duplicates in the list of ranks.

## 17.2.190.6. 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.

See also

MPI_Group_compare