[MPI3-IO] [EXTERNAL] New MPI-IO routines

Lofstead, Gerald F II gflofst at sandia.gov
Thu May 24 15:08:51 CDT 2012

I can see the usefulness of this beyond the SWMR case (essentially queue a
bunch of IO ops in the background and come back when they are all done)
and wonder is there a broader agenda that should be looked at for this?
For example, is the non-blocking, but ordered idea something useful for
messaging as well? Personally, I think so. Given that, is it worth
exploring this in a broader context to add the non-blocking, ordered style
to MPI as a whole?

Other than an explicit queue mechanism to execute these in series, what
are the complexity problems you envision? It seems really straightforward.

Jay Lofstead

On 5/24/12 12:39 PM, "Mohamad Chaarawi" <chaarawi at hdfgroup.org> wrote:

>Hi all,
>We would like to get a discussion going on adding new routines to the
>standard that would support non-blocking but ordered access routines,
>and non-blocking ordered file manipulation routines. They would be two
>separate tickets but they share similar semantics.
>So basically what we would like is that when we call:
>1) iwrite_at()
>2) iread_at()
>3) iwrite_at()
>4) waitall()
>We would like to see the data accessed as if the calls were blocking.
>This could translate to something like:
>There is ofcourse no such thing as iwait, but you get the idea :-)
>Our use case for this is the SWMR functionality that is being worked on,
>where the non-blocking version would require the MPI library to remember
>the order in which the operations were called; otherwise I don't see how
>we can enforce this ordering and at the same time keep the entire I/O
>access nonblocking.
>We probably need to rename the routines (something other than the i
>prefix) because the semantics are different from the current
>non-blocking routines. Maybe aread/awrite (a for asynchronous).
>Another feature we are considering is the non-blocking file manipulation
>routines. Similarly to the semantics described above, the library needs
>to remember the order they are called.
>Again since the semantics are different in the way other immediate
>routines are defined, we need to reconsider the naming.
>Any thoughts?
>MPI3-IO mailing list
>MPI3-IO at lists.mpi-forum.org

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