The Great and Terrible implementation of MPI-2

function index


Frees an info object
int MPI_Info_free(
  MPI_Info *info


[in] info object to be freed (handle)


This function frees info and sets it to MPI_INFO_NULL. The value of an info argument is interpreted each time the info is passed to a routine. Changes to an info after return from a routine do not affect that interpretation.

Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

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.
Invalid Info
Other error; use MPI_Error_string to get more information about this error code.

Example Code

The following sample code illustrates MPI_Info_free.

#include "mpi.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main( int argc, char *argv[] )
int errs = 0;
    MPI_Info info1, infodup;
int nkeys, nkeysdup, i, vallen, flag, flagdup;
char key[MPI_MAX_INFO_KEY], keydup[MPI_MAX_INFO_KEY];
char value[MPI_MAX_INFO_VAL], valdup[MPI_MAX_INFO_VAL];
    MPI_Init( &argc, &argv );
    MPI_Info_create( &info1 );
    MPI_Info_set( info1, "host", "" );
    MPI_Info_set( info1, "file", "runfile.txt" );
    MPI_Info_set( info1, "soft", "2:1000:4,3:1000:7" );
    MPI_Info_dup( info1, &infodup );
    MPI_Info_get_nkeys( infodup, &nkeysdup );
    MPI_Info_get_nkeys( info1, &nkeys );
    if (nkeys != nkeysdup) {
        printf( "Dup'ed info has a different number of keys; is %d should be %d\n", nkeysdup, nkeys );fflush(stdout);
    vallen = MPI_MAX_INFO_VAL;
for (i=0; i<nkeys; i++) {
        /* MPI requires that the keys are in the same order after the dup */
        MPI_Info_get_nthkey( info1, i, key );
        MPI_Info_get_nthkey( infodup, i, keydup );
        if (strcmp(key, keydup)) {
            printf( "keys do not match: %s should be %s\n", keydup, key );fflush(stdout);
        vallen = MPI_MAX_INFO_VAL;
        MPI_Info_get( info1, key, vallen, value, &flag );
        MPI_Info_get( infodup, keydup, vallen, valdup, &flagdup );
        if (!flag || !flagdup) {
            printf( "Info get failed for key %s\n", key );fflush(stdout);
else if (strcmp( value, valdup )) {
            printf( "Info values for key %s not the same after dup\n", key );fflush(stdout);
    /* Change info and check that infodup does NOT have the new value (ensure that lazy dups are still duped) */
    MPI_Info_set( info1, "path", "/a:/b:/c/d" );
    MPI_Info_get( infodup, "path", vallen, value, &flag );
if (flag) {
        printf( "inserting path into info changed infodup\n" );fflush(stdout);

    MPI_Info_free( &info1 );
    MPI_Info_free( &infodup );

return errs;