Unfortunately even the canonical representation cannot make any
promises about either of these operations.
The canonical representation allows a file written by MPI-IO on one
machine to be read by MPI-IO on another machine. It does not make any
statements about reading such a file from a non MPI-IO environment.
The reason for this omission is that there are many native file
formats (particularly for files written from Fortran), and therefore
MPI cannot be both canonical and inter-operable.
The simplest solution which is guaranteed to work is very likely going
to remain "read on one process using MPI-IO, and write using the
normal mechanism".
While this is a depressing conclusion, please note that this is *not*
an MPI problem, but an existing problem that MPI happens to have
bumped into.
-- Jim
James Cownie
Dolphin Interconnect Solutions
Phone : +44 117 9071438
E-Mail: jcownie@dolphinics.com