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Subject: [OMPI users] Tuned collectives: How to choose them dynamically? (-mca coll_tuned_dynamic_rules_filename dyn_rules)"
From: Gus Correa (gus_at_[hidden])
Date: 2009-07-22 23:48:39


Dear OpenMPI experts

I would like to experiment with the OpenMPI tuned collectives,
hoping to improve the performance of some programs we run
in production mode.

However, I could not find any documentation on how to select the
different collective algorithms and other parameters.
In particular, I would love to read an explanation clarifying
the syntax and meaning of the lines on "dyn_rules"
file that is passed to
"-mca coll_tuned_dynamic_rules_filename ./dyn_rules"

Recently there was an interesting discussion on the list
about this topic. It showed that choosing the right collective
algorithm can make a big difference in overall performance:

http://www.open-mpi.org/community/lists/users/2009/05/9355.php
http://www.open-mpi.org/community/lists/users/2009/05/9399.php
http://www.open-mpi.org/community/lists/users/2009/05/9401.php
http://www.open-mpi.org/community/lists/users/2009/05/9419.php

However, the thread was concentrated on "MPI_Alltoall".
Nothing was said about other collective functions.
Not much was said about the
"tuned collective dynamic rules" file syntax,
the meaning of its parameters, etc.

Is there any source of information about that which I missed?
Thank you for any pointers or clarifications.

Gus Correa
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Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA
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