.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.TH MPI_Init 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"

.SH NAME
\fBMPI_Init\fP \- Initializes the MPI execution environment

.SH SYNTAX
.ft R

.SH C Syntax
.nf
#include <mpi.h>
int MPI_Init(int *\fIargc\fP, char ***\fIargv\fP)

.fi
.SH Fortran Syntax
.nf
INCLUDE 'mpif.h'
MPI_INIT(\fIIERROR\fP)
	INTEGER	\fIIERROR\fP 

.fi
.SH C++ Syntax
.nf
#include <mpi.h>
void MPI::Init(int& \fIargc\fP, char**& \fIargv\fP)
void MPI::Init()

.fi
.SH INPUT PARAMETERS
.ft R
.TP 1i
argc
C/C++ only: Pointer to the number of arguments.
.TP 1i
argv
C/C++ only: Argument vector.

.SH OUTPUT PARAMETER
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer). 

.SH DESCRIPTION
.ft R
This routine, or MPI_Init_thread, must be called before any other MPI
routine (apart from MPI_Initialized) is called. MPI can be initialized
at most once; subsequent calls to MPI_Init or MPI_Init_thread are
erroneous.
.sp
All MPI programs must contain a call to MPI_Init or
MPI_Init_thread. Open MPI accepts the C/C++ \fIargc\fP and \fIargv\fP
arguments to main, but neither modifies, interprets, nor distributes
them:
.sp
.nf
	{
		/* declare variables */
		MPI_Init(&argc, &argv);
		/* parse arguments */
		/* main program */ 
		MPI_Finalize();
	}
.fi

.SH NOTES
.ft R
The Fortran version does not have provisions for \fIargc\fP and
\fIargv\fP and takes only IERROR.
.sp
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.

.SH ERRORS
.ft R
Almost all MPI routines return an error value; C routines as
the value of the function and Fortran routines in the last argument. C++
functions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does not
guarantee that an MPI program can continue past an error. 
.sp
See the MPI man page for a full list of MPI error codes.

.SH SEE ALSO
.ft R
.nf
MPI_Init_thread
MPI_Initialized
MPI_Finalize