Rob,
Thank you for your informative reply. I had no luck finding the
external32 data representation in any of several mpi implementations and
thus I do need to devise an alternative strategy. Do you know of a good
reference explaining how to combine HDF5 with mpi?
---Tom
Robert Latham wrote:
On Mon, Jan 08, 2007 at 02:32:14PM -0700, Tom Lund wrote:
Rainer,
Thank you for taking time to reply to my querry. Do I understand
correctly that external32 data representation for i/o is not
implemented? I am puzzled since the MPI-2 standard clearly indicates
the existence of external32 and has lots of words regarding how nice
this feature is for file interoperability. So do both Open MPI and
MPIch2 not adhere to the standard in this regard? If this is really the
case, how difficult is it to define a custom data representation that is
32-bit big endian on all platforms? Do you know of any documentation
that explains how to do this?
Thanks again.
Hi Tom
You do understand correctly. I do not know of an MPI-IO
implementation that supports external32.
When you say "custom data representation" do you mean an MPI-IO
user-defined data representation?
An alternate approach would be to use a higher level library like
parallel-netcdf or HDF5 (configured for parallel i/o). Those
libraries already define a file format and implement all the necessary
data conversion routines, and they have a wealth of ancilary tools and
programs to work with their respective file formats. Additionally,
those higher-level libraries will offer you more features than MPI-IO
such as the ability to define atributes on variables and datafiles.
Even better, there is the potential that these libraries might offer
some clever optimizations for your workload, saving you the effort.
Further, you can use those higher-level libraries on top of any MPI-IO
implementation, not just OpenMPI or MPICH2.
This is a little bit of a diversion from your original question, but
to sum it up, I'd say one potential answer to the lack of external32
is to use a higher level library and sidestep the issue of MPI-IO data
representations altogether.
==rob
--
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Thomas S. Lund
Sr. Research Scientist
Colorado Research Associates, a division of
NorthWest Research Associates
3380 Mitchell Ln.
Boulder, CO 80301
(303) 415-9701 X 209 (voice)
(303) 415-9702 (fax)
l...@cora.nwra.com
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