[MPI3 Fortran] Nonblocking MPI and Fortran temporary memory modifications

[Rasmussen, Craig E]

We've had several discussions regarding the use of ASYNCHRONOUS for the usage required by MPI on the J3 committee.  Some members thought that ASYNCHRONOUS shouldn't be used apart from I/O.  However, a vote was taken and a large majority voted that the ASYNCHRONOUS attribute should be used for this purpose.

So the question is not about whether a compiler implements ASYNCHRONOUS I/O but whether it respects the ASYNCHRONOUS semantics.  Perhaps we need an interp request to formalize this beyond a simple J3 member vote.

-craig


On Mar 27, 2011, at 3:34 AM, Rolf Rabenseifner wrote:

> Dear all,
> 
> Reinhold showed me that the ASYNCHRONOUS attribute may not help
> because a compiler may implement asynchronous Fortran I/O
> with blocking I/O and therefore may ignore all ASYNCHRONOUS 
> attributes.
> 
> Please have a look at  
> https://svn.mpi-forum.org/trac/mpi-forum-web/attachment/ticket/229/mpi-report-F2008-2011-03-26-changeonly-majorpages.pdf
> 
> Pages 24-31 in the pdf (pages 549-556 in the original document)
> show our knowledge about the nonblocking and datatype (MPI_BOTTOM) problems
> in the combination of Fortran and MPI.
> 
> Unfortunately in the taböle on page 550, we have to modify all entries
> about ASYNCHRONOUS into "NOT solved".
> 
> Do you see further solutions?
> 
> Do you see further problems with nonblocking and "MPI_BOTTOM", 
> that are not mentioned in this section and that should be.
> 
> Is the rest of this section correct?
> If something is incorrect, it would be important to understand why.
> 
> I've reworked this section based on many discussions and on my best 
> knowledge - but I'm not sure whether this was enough.
> 
> Best regards
> Rolf
> 
> 
> -- 
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
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