.TH MPI_Init 3 "11/12/2019" " " "MPI"

.SH NAME

MPI_Init \-  Initialize the MPI execution environment 

.SH SYNOPSIS

.nf

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

.fi

.SH INPUT PARAMETERS

.PD 0

.TP

.B argc 

- Pointer to the number of arguments

.PD 1

.PD 0

.TP

.B argv 

- Pointer to the argument vector

.PD 1

.SH THREAD AND SIGNAL SAFETY

This routine must be called by one thread only.  That thread is called

the 

.B main thread

and must be the thread that calls 

.I MPI_Finalize

\&.

.SH NOTES

The MPI standard does not say what a program can do before an 

.I MPI_INIT

or

after an 

.I MPI_FINALIZE

\&.

In the MPICH implementation, you 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 NOTES FOR C

As of MPI-2, 

.I MPI_Init

will accept NULL as input parameters. Doing so

will impact the values stored in 

.I MPI_INFO_ENV

\&.

.SH NOTES FOR FORTRAN

The Fortran binding for 

.I MPI_Init

has only the error return

.nf

subroutine MPI_INIT(ierr)

integer ierr

.fi

.SH ERRORS

All MPI routines (except 

.I MPI_Wtime

and 

.I MPI_Wtick

) return an error value;

C routines as the value of the function and Fortran routines in the last

argument.  Before the value is returned, the current MPI error handler is

called.  By default, this error handler aborts the MPI job.  The error handler

may be changed with 

.I MPI_Comm_set_errhandler

(for communicators),

.I MPI_File_set_errhandler

(for files), and 

.I MPI_Win_set_errhandler

(for

RMA windows).  The MPI-1 routine 

.I MPI_Errhandler_set

may be used but

its use is deprecated.  The predefined error handler

.I MPI_ERRORS_RETURN

may be used to cause error values to be returned.

Note that MPI does 

.B not

guarentee that an MPI program can continue past

an error; however, MPI implementations will attempt to continue whenever

possible.

.PD 0

.TP

.B MPI_SUCCESS 

- No error; MPI routine completed successfully.

.PD 1

.PD 0

.TP

.B MPI_ERR_OTHER 

- This error class is associated with an error code that 

indicates that an attempt was made to call 

.I MPI_INIT

a second time.

.I MPI_INIT

may only be called once in a program.

.PD 1

.SH SEE ALSO

MPI_Init_thread, MPI_Finalize

.br