[Mpi3-hybridpm] [EXTERNAL] Re: Threading homeworking / next telecon

William Gropp wgropp at illinois.edu
Mon Mar 25 15:17:59 CDT 2013

I was only addressing the issue of calling the thread level routines before knowing what thread level you had.

I'm not sure what you are looking for.  In the case of MPI_THREAD_MULTIPLE, an implementation can provide significant concurrency today without any change in the MPI standard - that's a major reason for that table (more to the point - this table is meant as a guide for not using locks).  Can you give me an example of something that the current MPI semantics prohibits that you'd like to achieve with MPI_THREAD_PER_OBJECT?  


William Gropp
Director, Parallel Computing Institute
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Thomas M. Siebel Chair in Computer Science
University of Illinois Urbana-Champaign

On Mar 25, 2013, at 2:53 PM, Jeff Hammond wrote:

> That doesn't do much for me in terms of enabling greater concurrency
> in performance-critical operations.
> I'd like to propose that we try to make all of "Access Only", "Update
> RefCount", "Read of List" and "None" thread safe in all cases.  All of
> these are read-only except for "Update RefCount", but this can be done
> with atomics.  I am assuming that concurrent reads are only permitted
> to happen after the writing calls on the object have completed.  This
> is the essence of MPI_THREAD_PER_OBJECT.
> Jeff

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