# 17.2.325. MPI_Session_get_nth_pset

MPI_Session_get_nth_pset — Query runtime for name of the nth process set

## 17.2.325.1. SYNTAX

### 17.2.325.1.1. C Syntax

    #include <mpi.h>

    int MPI_Session_get_nth_pset(MPI_Session session, MPI_Info info, int n, int *pset_len, char *pset_name)

### 17.2.325.1.2. Fortran Syntax

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

    MPI_SESSION_GET_NTH_PSET(SESSION, INFO, N, PSET_LEN, PSET_NAME, IERROR)
        INTEGER SESSION, INFO, N, PSET_LEN, IERROR
        CHARACTER*(*) PSET_NAME

### 17.2.325.1.3. Fortran 2008 Syntax

    USE mpi_f08

    MPI_Session_get_nth_pset(session, info, n, pset_len, pset_name, ierror)
        TYPE(MPI_Session), INTENT(IN) :: session
        TYPE(MPI_Info), INTENT(IN) :: info
        INTEGER, INTENT(IN) :: n
        INTEGER, INTENT(INOUT) :: pset_len
        CHARACTER(LEN=*), INTENT(OUT) :: pset_name
        INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 17.2.325.2. INPUT PARAMETERS

- `session` : session (handle)

- `info` : info object (handle)

- `n` : index of the desired process set name (integer)

### 17.2.325.2.1. INPUT/OUTPUT PARAMETER

- `pset_len` : length of the pset_name argument (integer)

## 17.2.325.3. OUTPUT PARAMETERS

- `pset_name` : name of the nth process set (string)

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

## 17.2.325.4. DESCRIPTION

MPI_Session_get_nth_pset returns the name of the nth process set in the supplied pset_name buffer. pset_len is the size of the buffer needed to store the nth process set name. If the pset_len passed into the function is less than the actual buffer size needed for the process set name, then the string value returned in pset_name is truncated. If pset_len is set to 0, pset_name is not changed. On return, the value of pset_len will be set to the required buffer size to hold the process set name. In C, pset_len includes the required space for the null terminator. In C, this function returns a null terminated string in all cases where the pset_len input value is greater than 0.

## 17.2.325.5. NOTES

Process set names have an implementation-defined maximum length of MPI_MAX_PSET_NAME_LEN characters. MPI_MAX_PSET_NAME_LEN shall have a value of at least 63.

## 17.2.325.6. 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_Session_init