Subject: I/O - what else

From: Piyush Mehrotra <[email-masked]>
Date: Wed, 24 Jun 92 16:23:53 -0400

During the discussions in the plenary meetings I have heard the sentiment
that Fortran I/O is good enough - we don't need anything else.
Am I correct in presuming that the semantics of writing out a distributed
array to a file is as follows:
	write the file out in fortran column major serial order
	such that even a sequential fortran program can read it back in

This semantics does not allow the distributed array to be output
keeping the distribution of the array in mind.  For example,
if an array needs to be written out temporarily before being read
in into another with the same distribution, then I would prefer
that each processor write out its local portion of the array
(possibily after serialising it) independently.  This would
most likely be able to exploit multiple I/O controllers and
would also avoid the expense of redistributing the array
before writing it out and after reading it in.
The same situation may arise if I am pssing data between two
HPF programs without ever reading it in a sequential program.

Is this something we should look at and provide for? Actually
I do know of at least one user here on the iPSC who does exactly
what I have described above.

Comments?

	- Piyush

---

From: [email-masked] (Alok Choudhary)
Date: Wed, 24 Jun 92 16:29:26 EDT

I agree with Piyush. I have given it some thought, but not enough yet
to concretely propose something. But I am in favor of providing
directives to help improve I/O.

Alok

 Alok Choudhary
 Assistant Professor
 ECE Dept., 121 Link Hall
 Syracuse University
 Syracuse, NY 13244
 (315)-443-4280
 Fax: (315)-443-2583
 [email-masked]