# 17.2.74. MPI_Comm_set_info

MPI_Comm_set_info — Set communicator info hints

## 17.2.74.1. SYNTAX

### 17.2.74.1.1. C Syntax

    #include <mpi.h>

    int MPI_Comm_set_info(MPI_Comm comm, MPI_Info info)

### 17.2.74.1.2. Fortran Syntax

    USE MPI
    ! or the older form: INCLUDE 'mpif.h'
    MPI_COMM_SET_INFO(COMM, INFO, IERROR)
         INTEGER COMM, INFO, IERROR

### 17.2.74.1.3. Fortran 2008 Syntax

    USE mpi_f08
    MPI_Comm_set_info(comm, info, ierror)
         TYPE(MPI_Comm), INTENT(IN) :: comm
         TYPE(MPI_Info), INTENT(IN) :: info
         INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 17.2.74.2. INPUT PARAMETERS

- `comm`: Communicator on which to set info hints

- `info`: Info object containing hints to be set on comm

## 17.2.74.3. OUTPUT PARAMETERS

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

## 17.2.74.4. DESCRIPTION

MPI_Comm_set_info sets new values for the hints of the communicator associated with comm. MPI_Comm_set_info is a collective routine. The info object may be different on each process, but any info entries that an implementation requires to be the same on all processes must appear with the same value in each process’s info object.

The following info key assertions may be accepted by Open MPI:

mpi_assert_no_any_tag (boolean): If set to true, then the implementation may assume that the process will not use the `MPI_ANY_TAG` wildcard on the given communicator.

mpi_assert_no_any_source (boolean): If set to true, then the implementation may assume that the process will not use the `MPI_ANY_SOURCE` wildcard on the given communicator.

mpi_assert_exact_length (boolean): If set to true, then the implementation may assume that the lengths of messages received by the process are equal to the lengths of the corresponding receive buffers, for point-to-point communication operations on the given communicator.

mpi_assert_allow_overtaking (boolean): If set to true, then the implementation may assume that point-to-point communications on the given communicator do not rely on the non-overtaking rule specified in MPI-3.1 Section 3.5. In other words, the application asserts that send operations are not required to be matched at the receiver in the order in which the send operations were performed by the sender, and receive operations are not required to be matched in the order in which they were performed by the receiver.

## 17.2.74.5. 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.

See also

- MPI_Comm_get_info

- MPI_Info_create

- MPI_Info_set

- MPI_Info_free