[MPI3 Fortran] Request for a straw vote.

Craig Rasmussen crasmussen at newmexicoconsortium.org
Fri Jun 12 12:17:19 CDT 2009

On Jun 12, 2009, at 3:52 AM, Supalov, Alexander wrote:

> Hi,
> Complementing Steve's reply that represents Intel's position, there  
> may be two additional aspects to consider, namely:
> 1. We may want to decide what flavor of the new Fortran interface  
> we're striving at. There are at least two extremes:
> 	a. As close as possible to the C interface with all its low level  
> efficiency

This is the choice for the MPI standard.  There has been some  
discussion of this in earlier emails.  I'll let Jeff answer if you  
would like a recap.

> 	b. As natural as possible for Fortran with all its modern  
> expressive power

I'm going to work on an additional MPI API and reference  
implementation that will be outside of the MPI standard (like Boost  
MPI is for C++).  I'm happy to have additional cooks.

> We may even want to formulate two different interfaces according to  
> these extremes, and see what they look like, both in theory and in  
> practice. I would even propose a usability review with the  
> application programmers. Then we may be better equipped to find a  
> golden middle between the extremes, or at least consistently go for  
> one of the extremes if it proves superior to the other.
> 2. As soon as the MPI standard allows certain features to be  
> expressed in a compiler dependent way, even for a while (the any- 
> type-and-shape comes to mind here first and foremost), one is  
> exposed to the possible subtle semantical variations between  
> different compilers, as well as between the compiler ways and the  
> final standard. This may lead to dissatisfied customers who will  
> notice that when they change the compiler/MPI implementation, the  
> behavior of their applications may change as well.
> Note that even if we try to specify very precisely what we want from  
> the Fortran standard, and then, for any reason, the Fortran standard  
> committee decides to go a different way, we may be basically left  
> with an MPI interface that is difficult to impossible to represent  
> faithfully in a Fortran standard compliant manner.
> Hence, it may be advisable to wait until the respective Fortran  
> standard syntax and semantics are cast in stone. As we're talking  
> about MPI-3 here, we may have some time for this slower, safer  
> approach I hope.

Yup, the MPI-3 Fortran interfaces will wait on the Fortran standard to  
be finalized so this won't be a problem.  The earliest any MPI-3 stuff  
could come out would be when the leaves fall in 2010.



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