Retrieves attribute value by key
int MPI_Attr_get ( comm, keyval, attr_value, flag )
- comm - communicator to which attribute is attached (handle)
- keyval - key value (integer)
- attr_value - attribute value, unless flag = false
- flag - true if an attribute value was extracted; false if no attribute is
associated with the key
Attributes must be extracted from the same language as they were inserted
in with MPI_ATTR_PUT. The notes for C and Fortran below explain why.
Notes for C
Even though the attr_value arguement is declared as void *, it is
really the address of a void pointer. See the rationale in the
standard for more details.
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
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER
The attr_value in Fortran is a pointer to a Fortran integer, not
a pointer to a void *.
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_Errhandler_set; 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
- MPI_SUCCESS - No error; MPI routine completed successfully.
- MPI_ERR_COMM - Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank).
- MPI_ERR_OTHER - Other error; the error code associated with this error
indicates an attempt to use an invalue keyval.