WHAT: Rename the --enable-*-threads configure switches and ENABLE*THREAD*
macros.
(see previous RFC:
http://www.open-mpi.org/community/lists/devel/2010/01/7366.php)
WHY: The fact that thread safety in OPAL and ORTE requires a configure switch
with "mpi" in the name is very non-intuitive. Additionally,
MPI_THREAD_MULTIPLE support is not necessarily the same thing as OPAL thread
support (MTM needs OPAL thread support, but not the other way around), and we
are seeing a growing advantage/need for ORTE to utilize threads in mpirun and
orted irrespective of the MPI layer's threading abilities.
WHERE: Mostly opal/config/opal_config_threads.m4, something new in
ompi/config/*.m4, and wherever the current ENABLE*THREAD* macros are currently
used in the current code base.
WHEN: Next Friday COB
TIMEOUT: COB, Friday, Feb 5, 2010
------------------------
More details:
Cisco is starting to investigate using ORTE and OPAL in various threading
scenarios. The fact that you need to enable thread safety in ORTE/OPAL with a
configure switch that has the word "mpi" in it is extremely counter-intuitive
(it bit some of our engineers very badly, and they were mighty annoyed!!). In
addition, we ran into problems where it was advantageous to have threads in
ORTE, but we couldn't do it without forcing thread support into the MPI layer
because the switch is universal.
Since this functionality actually has nothing to do with MPI (it's actually the
other way around -- MPI_THREAD_MULTIPLE needs this functionality), we really
should divorce MPI threading functionality from whether threading machinery is
enabled in OPAL or not.
These names were proposed at the end of the previous RFC and no one objected,
so I'm sending this around as a new RFC to ensure we're all on the same sheet
of music:
--enable-opal-progress-threads: enables progress thread machinery in opal
--> this is just a renaming from --enable-progress-threads
--> the corresponding #define stays the same: OPAL_ENABLE_PROGRES_THREADS
--enable-opal-multi-threads: enables multi threaded machinery in opal
--> this is just a renaming from --enable-mpi-threads
--> the corresponding #define also renames; from OPAL_ENABLE_MPI_THREADS to
OPAL_ENABLE_MULTI_THREADS
--enable-mpi-thread-multiple: enables the use of MPI_THREAD_MULTIPLE; *ONLY*
affects the MPI layer
--> use of this switch explicitly implies --enable-opal-multi-threads
--> new #define: OMPI_ENABLE_THREAD_MULTIPLE
We can keep and deprecate the old configure options if desired:
--enable-mpi-threads: deprecated synonym for --enable-mpi-thread-multiple
--enable-progress-threads: deprecated synonym for --enable-opal-progress-threads
..although I'm somewhat inclined to ditch them unless someone has strong
feelings about keeping them.
Doing the name change in OPAL and ORTE is fairly straightforward -- it's
essentially an s/foo/bar/g kind of operation. It'll likely take a little more
effort in the MPI layer because the places where the current #defines are used
may need to switch to the new name or to the new OMPI_ENABLE_THREAD_MULTIPLE
name (and maybe some new logic? I am not sure without looking into it closer).
--
Jeff Squyres
jsquy...@cisco.com
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http://www.cisco.com/web/about/doing_business/legal/cri/
