In short, the Canonical (or External) representation(s) together with import/
export (and in a high-quality implementaion, retention of seek addresses) gives
the user a strong clue as to what is in a sequential file. Hopefully the user
will only have to resort to "read on one process using MPI-IO, and write using
the normal mechanism" on a very small number of "low quality" implementations.
Leslie Hart (hart@fsl.noaa.gov)
>
> Albert points out the desire to be able to read files written with
> MPI/IO on sequential machines, or read files written on sequential
> machines via MPI-IO.
>
> 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
>