[Mpi-forum] Request introspection

[William Gropp]

There are already requests for I/O operations on files (just not  
collective nonblocking file I/O).

For a tool, this isn't detailed enough - given a request at random,  
even for point-to-point, whether it is a send or receive, and whether  
it is persistent or not, is important.

However, requests are also on the critical path for performance.  I'm  
opposed to anything that adds yet more overhead; there are also  
alternatives for tools to use (though they require much more work on  
the part of the tool developer).

Bill

On Aug 1, 2011, at 6:50 PM, Jeff Squyres wrote:

> MPI now has 3 different types of requests that I can think of, with  
> pending proposals for (at least) 2 more:
>
> - point-to-point
> - collective
> - generalized
> - timers (proposed)
> - file (proposed)
>
> Would it be worthwhile to have a simple introspection routine that  
> can return an enum telling you the type of a request handle?  E.g.,  
> MPI_REQUEST_GET_TYPE that has an OUT parameter that will be set to  
> MPI_REQUEST_PT2PT, MPI_REQUEST_COLLECTIVE, MPI_REQUEST_GENERALIZED,  
> etc.
>
> I can generally see how this might be useful to applications, but I  
> can't think of a "must have" kind of use case.
>
> Does anyone else think that this would be valuable / useful?
>
> -- 
> Jeff Squyres
> jsquyres at cisco.com
> For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
>
>
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William Gropp
Director, Parallel Computing Institute
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign