The Great and Terrible implementation of MPI-2

function index


Indicates whether MPI_Init has been called.
int MPI_Initialized(
  int *flag


[out] Flag is true if MPI_Init or MPI_Init_thread has been called and false otherwise.


This routine may be used to determine whether MPI_INIT has been called. It is the only MPI-1 routine that may be called before MPI_INIT is called.

Notes for Fortran

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.


All MPI routines (except MPI_Wtime and 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 MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

No error; MPI routine completed successfully.

Example Code

The following sample code illustrates MPI_Initialized.

#include "mpi.h"
#include <stdio.h>
int main( int argc, char *argv[] )
    int flag;
    flag = 0;
if (flag)
        printf("MPI_Initialized returned true before MPI_Init.\n");
        return -1;
    MPI_Init(&argc, &argv);
    flag = 0;
if (!flag)
        printf("MPI_Initialized returned false after MPI_Init.\n");
        MPI_Abort(MPI_COMM_WORLD, error);
return -1;
return 0;