The Great and Terrible implementation of MPI-2

function index


Return a string for a given error code
int MPI_Error_string(
  int errorcode,
  char *string,
  int *resultlen

int MPI_Error_string(
  int errorcode,
  wchar_t *string,
  int *resultlen


[in] Error code returned by an MPI routine or an MPI error class
[out] Text that corresponds to the errorcode
[out] Length of string

Notes: Error codes are the values return by MPI routines (in C) or in the ierr argument (in Fortran). These can be converted into error classes with the routine MPI_Error_class.


Returns the error string associated with an error code or class. The argument string must represent storage that is at least MPI_MAX_ERROR_STRING characters long.

The number of characters actually written is returned in the output argument, resultlen.


The form of this function was chosen to make the Fortran and C bindings similar. A version that returns a pointer to a string has two difficulties. First, the return string must be statically allocated and different for each error message (allowing the pointers returned by successive calls to MPI_ERROR_STRING to point to the correct message). Second, in Fortran, a function declared as returning CHARACTER*(*) can not be referenced in, for example, a PRINT statement.

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 argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).

Example Code

The following sample code illustrates MPI_Error_string.

#include "mpi.h"
#include <stdio.h>

int main(int argc, char *argv[])
    int rank, nprocs, error, eclass, len;
    char estring[MPI_MAX_ERROR_STRING];

/* Make an invalid call to generate an error */
    error = MPI_Bcast(NULL, 0, MPI_INT, -1, MPI_COMM_WORLD);
    MPI_Error_class(error, &eclass);
    MPI_Error_string(error, estring, &len);
    printf("Error %d: %s\n", eclass, estring);fflush(stdout);
return 0;