On Thu, Nov 19, 2015 at 1:14 PM, Rob Latham <robl@mcs.anl.gov> wrote:


On 11/19/2015 03:01 PM, Jeff Hammond wrote:
That is so cool!  Do you have psychic powers or did you actually go from
email to finished code in 65 minutes?

 Pavan maybe has the psychic powers?  he asked  me work on this a couple months ago.


That makes sense.  Pavan did a Vulcan mind meld on me before I left Argonne :-)
 
but the two implementations have made interesting design choice: OpenMPI went with the "add a lot of flags" approach.  Pavan suggested we take an approach that introduces only one new flag (MPIX_COMM_SPLIT_NEIGHBORHOOD) but then uses an info argument to indicate *how* that neighborhood split should occur.


I strongly favor the info approach, since it is much easier to toggle features on and off as appropriate without thrashing the header.

If MPICH were to support all the HWLOC options like OpenMPI, having it inside of an info key would be future-proof w.r.t. HWLOC feature changes, unlike an explicit list of types.  It also makes it trivial to match the exact syntax of HWLOC commands since info keys are composed of strings.
 
As far as an implementation is concerned, both approaches are equivalent.


Indeed.
 
As an end-user, Jeff, do you have an opinion (hah! oh, I kill me... I thought I could type that with a straight face, I really did...) on which approach you prefer?


I have no opinions, just facts that others have yet to accept as truth ;-)

Jeff
 
==rob

Jeff

On Thu, Nov 19, 2015 at 12:39 PM, Rob Latham <robl@mcs.anl.gov
 <mailto:robl@mcs.anl.gov>> wrote:



    On 11/19/2015 01:34 PM, Jeff Hammond wrote:

        https://github.com/open-mpi/ompi/pull/320 implements features
        related to
        what was proposed in
        https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/297 and
        https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/372.

        It would be nice if MPICH supported such things as well.  Since
        MPICH
        also uses HWLOC, I imagine it is not too difficult.

        I will file a ticket about this in the absence of objections.



    BLAMMO!

    http://git.mpich.org/mpich-dev.git/shortlog/refs/heads/comsplit_commonfs

    ==rob


        Thanks,

        Jeff

        --
        Jeff Hammond
        jeff.science@gmail.com <mailto:jeff.science@gmail.com>
         <mailto:jeff.science@gmail.com <mailto:jeff.science@gmail.com>>

        http://jeffhammond.github.io/


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    Rob Latham
    Mathematics and Computer Science Division
    Argonne National Lab, IL USA
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--
Jeff Hammond
jeff.science@gmail.com <mailto:jeff.science@gmail.com>
http://jeffhammond.github.io/


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Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA
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Jeff Hammond
jeff.science@gmail.com
http://jeffhammond.github.io/