[MPI3-IO] shared file pointer

[Torsten Hoefler]

On Wed, Feb 01, 2012 at 02:48:16PM -0600, Quincey Koziol wrote:
> > I would have to look up if this is the way the standard looks at it, but
> > one possible way of reasoning about the non-blocking collectives is to
> > consider them to be blocking from the time they are started up to the time
> > they are completed by wait/test/...
> > 
> > In this case, the example reduces to having two threads doing a
> > MPI_File_read_ordered on the same file handle.
> > 
> > It is perfectly valid to ask what happens in MPI 2.2 in this case.
> > 
> > Clearly, for the split collectives, doing this is /not/ legal as the
> > standard explicitly prohibits having more than one split collective on the
> > same file handle at the same time.
> > 
> > But really, somebody with better knowledge of the non-blocking collectives
> > should answer what happens if two MPI_Iscan operations are executed on the
> > same communicator.
> 
> 	Torsten?  (CC'd)
There are obviously no filehandles in NBC. The scan operations match in
issue-order and the buffers specified have to be disjunct (as for any
nonblocking communication in MPI). I.e., the two NBCs do not influence
each other from a correctness perspective.

Torsten

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Torsten Hoefler         | Performance Modeling and Simulation Lead
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