MPI\_GROUP\_FROM\_SESSION\_PSET(3) Open MPI MPI\_GROUP\_FROM\_SESSION\_PSET(3)

MPI\_Group\_from\_session\_pset — Creates a group using a provided session handle and process set.

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Group_from_session_pset(MPI_Session session, const char *pset_name, MPI_Group *newgroup)
```

## [Fortran Syntax](#Fortran_Syntax)

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_GROUP_FROM_SESSION_PSET(SESSION, PSET_NAME, NEWGROUP, IERROR)


    INTEGER SESSION,  NEWGROUP, IERROR


    CHARACTER*(*) PSET_NAME
```

## [Fortran 2008 Syntax](#Fortran_2008_Syntax)

```
USE mpi_f08
MPI_Group_from_session_pset(session, pset_name, newgroup, ierror)


    TYPE(MPI_Session), INTENT(IN) :: session


    CHARACTER(LEN=*), INTENT(IN) :: pset_name


    TYPE(MPI_Group), INTENT(OUT) :: newgroup


    INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

# [INPUT PARAMETERS](#INPUT_PARAMETERS)

- **session** : Session (handle).

[**pset\_name (name of process set to use to create the new group)**](#pset_name)

(string)

# [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS)

•

[**newgroup (New group derived from supplied session and process set)**](#newgroup)

(handle).

•

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

# [DESCRIPTION](#DESCRIPTION)

The function MPI\_Group\_from\_session\_pset creates a group newgroup using the provided session handle and process set. The process set name must be one returned from an invocation of MPI\_Session\_get\_nth\_pset &lt;#mpi-session-get-nth-pset&gt; using the supplied session handle. If the pset\_name does not exist, MPI\_GROUP\_NULL will be returned in the newgroup argument.

# [NOTE](#NOTE)

As with other group constructors, MPI\_Group\_from\_session\_pset is a local function.

# [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\_Session\_init &lt;#mpi-session-init&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

October 30, 2026

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Document: MPI_Group_from_session_pset(3) from openmpi-cuda-13.0 5.0.11-r1 (Chainguard OS)
Source: https://github.com/open-mpi/ompi