Since you say "a single text file", I would like to point out that MPI-IO doesn't support formatted I/O like fprintf. Only binary I/O. You can write character arrays as characters. Rajeev

-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rob Latham Sent: Tuesday, October 13, 2009 3:57 PM To: Henry Freund Cc: [email protected] Subject: Re: [mpich2-maint] ROMIO

On Tue, Oct 13, 2009 at 04:14:54PM -0500, Henry Freund wrote:

...

Is there any documentation for "romio". The issue is that I have a large amount of data on each processor that I would like to output to a single text file. Is it possible to have each processor write to a single file. The order of the writing is unimportant. I have been told that there are calls to a romio library that can do that. Yes?

Hi Henry Freund

What you want to do is definitely possible. First, a tiny bit of background. ROMIO is a library that implements a part of the MPI standard. the MPI-2 standard contains some I/O routines, which ROMIO implements. Nowadays, nearly every MPI library supports MPI-IO or MPI-2 so you shouldn't have to worry about finding or installing ROMIO

The MPI standard provides the details of the routines you'd have to make: http://www.mpi-forum.org/docs/mpi21-report-bw/node257.htm#Node257

The "Using MPI-2" book is the best resource for someone looking to learn more about MPI-IO features:

http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=3490

It sounds like you want something like "MPI_FILE_WRITE_AT_ALL".

==rob

-- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA _______________________________________________ mpich2-maint mailing list [email protected] https://lists.mcs.anl.gov/mailman/listinfo/mpich2-maint