NAME

       MPI_Attr_get -  Retrieves attribute value by key

SYNOPSIS

       int MPI_Attr_get(MPI_Comm comm, int keyval, void *attribute_val, int *flag)

INPUT PARAMETERS

       comm   - communicator to which attribute is attached (handle)
       keyval - key value (integer)

OUTPUT PARAMETERS

       attribute_val
              - attribute value, unless flag = false
       flag   - true if an attribute value was extracted;  false if no attribute is associated with the key

NOTES

       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 attribute_val argument is declared as void * , it is really the address of a void pointer
       (i.e., a void ** ).  Using a void * , however, is more in keeping with C idiom and allows the pointer  to
       be passed without additional casts.

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.

DEPRECATED FUNCTION

       The  MPI-2 standard deprecated a number of routines because MPI-2 provides better versions.  This routine
       is one of those that was deprecated.  The routine may continue to be used, but new code  should  use  the
       replacement routine.  The replacement for this routine is MPI_Comm_get_attr .

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.

       The attribute_val in Fortran is a pointer to a Fortran integer, not a pointer to a void * .

ERRORS

       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.

       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_KEYVAL
              - Invalid keyval

SEE ALSO

       MPI_Attr_put, MPI_Keyval_create, MPI_Attr_delete, MPI_Comm_get_attr

                                                    11/9/2015                                    MPI_Attr_get(3)