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MPI_Init.3.rst

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MPI_Init

MPI_Init Initializes the MPI execution environment

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Init(int *argc, char ***argv)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INIT(IERROR)
 INTEGER IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Init(ierror)
 INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

  • argc: C only: Pointer to the number of arguments.
  • argv: C only: Argument vector.

OUTPUT PARAMETER

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

DESCRIPTION

This routine, or MPI_Init_thread, must be called before most other MPI routines are called. There are a small number of errors, such as MPI_Initialized and MPI_Finalized. MPI can be initialized at most once; subsequent calls to MPI_Init or MPI_Init_thread are erroneous.

All MPI programs must contain a call to MPI_Init or MPI_Init_thread. Open MPI accepts the C argc and argv arguments to main, but neither modifies, interprets, nor distributes them:

/* declare variables */
MPI_Init(&argc, &argv);
/* parse arguments */
/* main program */
MPI_Finalize();

NOTES

The Fortran version does not have provisions for argc and argv and takes only IERROR.

The MPI Standard does not say what a program can do before an MPI_Init or after an MPI_Finalize. In the Open MPI implementation, it should do as little as possible. In particular, avoid anything that changes the external state of the program, such as opening files, reading standard input, or writing to standard output.

ERRORS

* MPI_Init_thread * MPI_Initialized * MPI_Finalize * MPI_Finalized