[Mpi-forum] Request introspection

Martin Schulz schulzm at llnl.gov
Tue Aug 2 12:01:40 CDT 2011

I tend to agree with Bill - sure, tools could use such information, but,
as Bill said, in most cases it is not sufficient information for tools
anyway and they need to track additional request information. Also,
most tools already have some kind of request tracking (since this
is needed for many use cases) and adding a field for the request
type to such a tracking mechanism is easy.


On Aug 2, 2011, at 8:33 AM, William Gropp wrote:

> 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  
>> 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
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Martin Schulz, schulzm at llnl.gov, http://people.llnl.gov/schulzm
CASC @ Lawrence Livermore National Laboratory, Livermore, USA

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