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MPI_COMM_GET_PARENT(3) Open MPI MPI_COMM_GET_PARENT(3)

MPI_Comm_get_parent — Returns the parent intercommunicator of current spawned process.

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Comm_get_parent(MPI_Comm *parent)


Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_GET_PARENT(PARENT, IERROR)


     INTEGER PARENT, IERROR


Fortran 2008 Syntax

USE mpi_f08
MPI_Comm_get_parent(parent, ierror)


     TYPE(MPI_Comm), INTENT(OUT) :: parent


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror


OUTPUT PARAMETERS

  • parent: The parent communicator (handle).
  • ierror: Fortran only: Error status (integer).

DESCRIPTION

If a process was started with MPI_Comm_spawn or MPI_Comm_spawn_multiple, MPI_Comm_get_parent returns the “parent” intercommunicator of the current process. This parent intercommunicator is created implicitly inside of MPI_Init and is the same intercommunicator returned by the spawn call made in the parents.

If the process was not spawned, MPI_Comm_get_parent returns MPI_COMM_NULL.

After the parent communicator is freed or disconnected, MPI_Comm_get_parent returns MPI_COMM_NULL.

NOTES

MPI_Comm_get_parent returns a handle to a single intercommunicator. Calling MPI_Comm_get_parent a second time returns a handle to the same intercommunicator. Freeing the handle with MPI_Comm_disconnect or MPI_Comm_free will cause other references to the intercommunicator to become invalid (dangling). Note that calling MPI_Comm_free on the parent communicator is not useful.

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_spawn
  • MPI_Comm_spawn_multiple



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December 2, 2024