[MPI3 Fortran] Nonblocking MPI and Fortran temporary memory modifications

Rasmussen, Craig E rasmussn at lanl.gov
Mon Mar 28 11:14:00 CDT 2011


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
> Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)





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