MPI\_GROUP\_INCL(3) Open MPI MPI\_GROUP\_INCL(3)

MPI\_Group\_incl — Produces a group by reordering an existing group and taking only listed members.

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Group_incl(MPI_Group group, int n, const int ranks[],


    MPI_Group *newgroup)
```

## [Fortran Syntax](#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
```

## [Fortran 2008 Syntax](#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
```

# [INPUT PARAMETERS](#INPUT_PARAMETERS)

- **group** : Group (handle).

[**n (Number of elements in array ranks (and size of)**](#n)

newgroup)(integer).

•

[**ranks (Ranks of processes in group to appear in newgroup (array of)**](#ranks)

integers).

# [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS)

•

[**newgroup (New group derived from above, in the order defined by)**](#newgroup)

ranks (handle).

•

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

# [DESCRIPTION](#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.

# [NOTE](#NOTE)

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

# [ERRORS](#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 &lt;#mpi-init&gt;/MPI\_Init\_thread &lt;#mpi-init-thread&gt;, after MPI\_Finalize &lt;#mpi-finalize&gt;, 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 &lt;#mpi-comm-set-errhandler&gt; 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 &lt;#mpi-comm-spawn&gt;/MPI\_Comm\_spawn\_multiple &lt;#mpi-comm-spawn-multiple&gt;. 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 &lt;#mpi-abort&gt; was called on that communicator. If called on a window or file, acts as if MPI\_Abort &lt;#mpi-abort&gt; 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 &lt;#mpi-comm-create-errhandler&gt; then MPI\_Comm\_set\_errhandler &lt;#mpi-comm-set-errhandler&gt;
- MPI\_File\_create\_errhandler &lt;#mpi-file-create-errhandler&gt; then MPI\_File\_set\_errhandler &lt;#mpi-file-set-errhandler&gt;
- MPI\_Session\_create\_errhandler &lt;#mpi-session-create-errhandler&gt; then MPI\_Session\_set\_errhandler &lt;#mpi-session-set-errhandler&gt; or at MPI\_Session\_init &lt;#mpi-session-init&gt;
- MPI\_Win\_create\_errhandler &lt;#mpi-win-create-errhandler&gt; then MPI\_Win\_set\_errhandler &lt;#mpi-win-set-errhandler&gt;

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

See the MPI man page &lt;#open-mpi&gt; for a full list of MPI error codes &lt;#open-mpi-errors&gt;.

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

**See also:**

MPI\_Group\_compare &lt;#mpi-group-compare&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

October 11, 2026

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Document: MPI_Group_incl(3) from openmpi-cuda-13.4 5.0.11-r1 (Chainguard OS)