[MPI3-IO] shared file pointer

[Rob Latham]

On Wed, Feb 22, 2012 at 05:25:04PM -0800, Adam T. Moody wrote:
> I will say, though, given that we can now have multiple outstanding
> non-blocking collective I/O calls, it would be really nice to be
> able to do the following:

> 
> MPI_File_iread_ordered()
> MPI_File_iread_ordered()
> MPI_File_iread_ordered()
> MPI_Waitall()
> 
> This provides a natural way for someone to read in three different
> sections from a file -- just issue all the calls and sit back and
> wait.  However, this can only be done if the pointer is updated in
> the initiation call.

Now we're getting somewhere.  Setting aside for a moment what the
letter of MPI-2.2 says, Adam's use case is exactly in line with the
spirit of shared file pointers.

The I/O can happen whenever but the bookeeping -- updating the shared
file pointer -- happens up front.

==rob

-- 
Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA