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MPI_COMM_SET_ATTR(3) Open MPI MPI_COMM_SET_ATTR(3)

MPI_Comm_set_attr — Stores attribute value associated with a key.

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Comm_set_attr(MPI_Comm comm, int comm_keyval, void *attribute_val)


Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_SET_ATTR(COMM, COMM_KEYVAL, ATTRIBUTE_VAL, IERROR)


     INTEGER COMM, COMM_KEYVAL, IERROR


     INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE_VAL


Fortran 2008 Syntax

USE mpi_f08
MPI_Comm_set_attr(comm, comm_keyval, attribute_val, ierror)


     TYPE(MPI_Comm), INTENT(IN) :: comm


     INTEGER, INTENT(IN) :: comm_keyval


     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: attribute_val


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror


INPUT/OUTPUT PARAMETER

•
comm: Communicator from which attribute will be attached (handle).

INPUT PARAMETERS

  • comm_keyval: Key value (integer).
  • attribute_val: Attribute value.

OUTPUT PARAMETER

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

DESCRIPTION

MPI_Comm_set_attr stores the stipulated attribute value attribute_val for subsequent retrieval by MPI_Comm_get_attr. If the value is already present, then the outcome is as if MPI_Comm_delete_attr was first called to delete the previous value (and the callback function delete_fn was executed), and a new value was next stored. The call is erroneous if there is no key with value comm_keyval; in particular MPI_KEYVAL_INVALID is an erroneous key value. The call will fail if the delete_fn function returned an error code other than MPI_SUCCESS.

This function replaces MPI_Attr_put, the use of which is deprecated. The C binding is identical. The Fortran binding differs in that attribute_val is an address-sized integer.

NOTES

Values of the permanent attributes MPI_TAG_UB, MPI_HOST, MPI_IO, and MPI_WTIME_IS_GLOBAL may not be changed.

The type of the attribute value depends on whether C or Fortran is being used. In C, an attribute value is a pointer (void *); in Fortran, it is a single, address-size integer system for which a pointer does not fit in an integer.

If an attribute is already present, the delete function (specified when the corresponding keyval was created) will be called.

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.

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April 11, 2024