[Mpi3-subsetting] no subset slot; action item I need your help with
Underwood, Keith D
keith.d.underwood at [hidden]
Sat Apr 26 11:47:18 CDT 2008
I thought the proposal for the surveys was more to open one discussion
area for the implementers and one discussion area for the users? Did
someone have something more in mind?
Keith
________________________________
From: mpi3-subsetting-bounces_at_[hidden]
[mailto:mpi3-subsetting-bounces_at_[hidden]] On Behalf Of
Supalov, Alexander
Sent: Saturday, April 26, 2008 2:41 AM
To: MPI 3.0 Sub-setting working group
Subject: Re: [Mpi3-subsetting] no subset slot;action item I need your
help with
Hi,
Draft report-out is available for comments, see
http://svn.mpi-forum.org/trac/mpi-forum-web/attachment/wiki/SubsettingWi
kiPage/MPI-3%20subsetting%2C%20take%202.pdf . Protected PDF is used to
meet Intel Legal requirement for external publications.
Updated proposal, see
http://svn.mpi-forum.org/trac/mpi-forum-web/wiki/Subsets, cites Jeff's
and Dick's MPI_Init ideas. Am looking for a link to Rainer's paper for
the compile time subsetting section.
If no-one will take on the surveys soon, we'll have to drop this idea.
Best regards.
Alexander
________________________________
From: Supalov, Alexander
Sent: Friday, April 25, 2008 9:13 PM
To: 'MPI 3.0 Sub-setting working group'
Subject: RE: no subset slot; action item I need your help with
Hi everybody,
I've done my action items to the best of ability and time available. See
the updated proposal in the Wiki.
Am still looking for a volunteer to organize the user and implementor
surveys.
I don't think we'll have a big report out - just a couple of slides on
the real progress. I'll do them on the plane.
See you in Chicago.
Alexander
________________________________
From: Supalov, Alexander
Sent: Tuesday, April 22, 2008 3:10 PM
To: 'MPI 3.0 Sub-setting working group'
Subject: no subset slot; action item I need your help with
Hi everybody,
Due to scheduling constraints, we're not going to have a special subset
slot during the coming MPI Forum meeting. For that we'll have about 2
hours to discuss MPI-3 structure where subsets should figure
prominently. If there's interest to talk subsets beyond this
opportunity, I suggest that we meet as a group at one of the dinners or
1:1 as we bump into each other.
Now, the action items from the last telecon. I need your help on one of
them:
- Create two query pages
- For users - what their minimum subset would look like
(functionality, performance)
- For implementors - what they can profit from (performance,
footprint)
I remember someone at the telecon had a very good suggestion about how
to formulate this. Can you take over this task now?
I'm about to engage on the following three and the final MPI-2.1 review:
- Alexander will add the description of the complexity matter
upfront to make readers see their favorite pain points
- Alexander will add the existing laundry list of controllable
features and ask for associated perf/footprint data
- Alexander will prepare to participate in the MPI-3 structure
discussion at the meeting
Best regards.
Alexander
________________________________
From: Supalov, Alexander
Sent: Wednesday, April 09, 2008 6:23 PM
To: 'MPI 3.0 Sub-setting working group'
Subject: RE: telecon, Wednesday, April 9, 8:00 am PDT/10:00 CDT/11:00
EDT/17:00 CEST
Hi everybody,
Thanks for your time today. Here's what we discussed (I captured what I
could, please add/modify):
Present: Richard Graham, David Gingold, Keith Underwood, Alexander
Supalov
- Opens
- Discussion of the proposal (see
http://svn.mpi-forum.org/trac/mpi-forum-web/wiki/Subsets)
- Complexity needs to be defined. Discussion on the aspects:
- Many people only use a few calls, don't need the rest; difficulty
of learning is related to this
- Sheer mass of the number of calls expected in MPI-3 may make
complexity unmanageable, requires hierarchy
- Performance implications are not considered primary motivation for
subsetting, but removing them may help
- E.g., extra cache effects may be induced by complexity (e.g.,
communicators)
- This can in principle be defeated by prioritization of the
hottest data fields
- We'll add the existing laundry list of things that may affect
performance
- Inviting people to quantify the performance benefits may help to
identify promising areas
- We may need hard facts to gauge potential performance gains
- We may need "fast stuff" subset people will safely be able to
use
- Making parts of the standard optional may be easier with subsets
- Dynamic processes seem to be a good example - some may disagree
- You may wait for the pull or create it; anyway, there's no big
pull on this in the volume market yet
- High end users are starting to use dynamic processes, though
- Selection at compile- link-, and runtime
- Compiler time is a little controversial, but there are already
some measurements that quantify this
- Link time comes in 3 forms
- Static linker is smart and will pull out of the .a only those
components the program uses
- Dynamic linker is not smart, but there's chance to either
- Do dlopen from within MPI to load extra modules (not
everyone's favorite), or
- Switch on/off parts of functionality in a bigger library -
this is where runtime comes in
- Runtime (MPI_Init and/or per-communicator basis)
- E.g., disabling MPI_ANY_SOURCE on a communicator may speed up
processing
- Should a program that runs on a subset also run on a full MPI
implementation? Probably, yes
- There's need to convince the community that subsetting is a good
idea, and portability will help
- There should be one standard but flexibility for MPI to adapt to a
particular set of applications
- If applications are portable across MPI, they won't actually care
of the rest of MPI
- The shape of MPI-3 may be strongly influenced by subsets
- The whole of the standard may be split into subsets, some of which
might be optional
- Vocal opponents may wrack subsets; we need hard data before we
bring this matter up
- Should subsets be predefined or should MPI provide a mechanism to
define them
- Think error handling: mechanism is there, as are several
predefined handlers; this model works
- Danger of proliferation of multiple mutually incompatible subsets
will increase with the mechanism definition
- Next steps
- Alexander will add the description of the complexity matter
upfront to make readers see their favorite pain points
- Alexander will add the existing laundry list of controllable
features and ask for associated perf/footprint data
- Alexander create two query pages
- For users - what their minimum subset would look like
(functionality, performance)
- For implementors - what they can profit from (performance,
footprint)
- Alexander will prepare to participate in the MPI-3 structure
discussion at the meeting
Best regards.
Alexander
________________________________
From: Supalov, Alexander
Sent: Tuesday, April 08, 2008 5:26 PM
To: 'MPI 3.0 Sub-setting working group'
Subject: telecon, Wednesday, April 9, 8:00 am PDT/10:00 CDT/11:00
EDT/17:00 CEST
Hi everybody,
This is a reminder: the subsetting telecon will be held on Wednesday,
April 9, 8:00 am PDT/10:00 CDT/12:00 EDT/17:00 CEST. The bridge details
are as follows:
Outside Intel: +1-916-356-2663, Inside Intel: 8-356-2663, Bridge: 5,
Passcode: 2603880
The primary goal will be to go thru the draft proposal available in the
Wiki (see http://svn.mpi-forum.org/trac/mpi-forum-web/wiki/Subsets), and
to see what we can report to the Forum end of April. Please send to me
additional agenda items you want to discuss.
Best regards.
Alexander
--
Dr Alexander Supalov
Intel GmbH
Hermuelheimer Strasse 8a
50321 Bruehl, Germany
Phone: +49 2232 209034
Mobile: +49 173 511 8735
Fax: +49 2232 209029
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