<div dir="ltr"><div><div>On Wed, Feb 10, 2016 at 12:44 AM, Daniel Holmes <span dir="ltr"><<a href="mailto:dholmes@epcc.ed.ac.uk" target="_blank">dholmes@epcc.ed.ac.uk</a>></span> wrote:<br></div></div><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Hi George,<br>
<br>
However, the effect on tools is not limited to global objects such
as the predefined communicators - the semantics are changed for
*any* communicator on which these info assertions are set. Your "and
tools" bit is therefore necessary but not sufficient.<br></div></blockquote><div><br></div>Assuming that the usual precautions are taken, aka. tools and libraries create their own communicators, I fail to see how the user hints on it's communicators can have any impact on libraries/tools ?<div><br></div><div>Moreover, as there is no way in MPI to get access to a communicator you don't see a reference (except MPI_COMM_WORLD and SELF), the user has no practical solution to set hints on a communicator that do no belong to her. The opposite is however always true. Because libraries and the tools have access to at least some of the application communicators, by setting hints on such a communicator (and in the case of tools we are talking about all communicators) they can affect the performance of the application.</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">I believe Jim has now changed the wording of the sentence you are
concerned about back to a previous version, i.e. "The usage of info
hints may also impact the effectiveness of tools." Does that
alleviate your concern?<br></div></blockquote><div><br></div><div>This is exactly the sentence that raise my concerns. Tools communicators are invisible to all other software layers in the application (obviously excluding other tools), and as such the particular sentence you mention has no meaning.</div><div><br></div><div> George.</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
<br>
Cheers,<br>
Dan.<div><div class="h5"><br>
<br>
<div>On 09/02/2016 22:36, George Bosilca
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Sorry to jump in the middle (or the end) of the
discussion. From my "MPI user" point of view, the last part of
the proposed advice is unsettling.
<div><br>
</div>
<div>"<span style="font-size:12.8px">The usage of some info
hints may allow the MPI library to change its behavior and,
as a result, impact the effectiveness of tools."</span></div>
<div><br>
</div>
<div>seems to have a broader scope, and includes application
developers, when the most obvious target should have been
tools developers. I think removing the last part and
emphasizing tools and libraries, makes a more clear point.</div>
<div><br>
</div>
<div><span style="font-size:12.8px">"Setting info hints on the
predefined communicators </span><span style="font-size:12.8px">\const</span><span style="font-size:12.8px">{</span><span style="font-size:12.8px">MPI</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">COMM</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">WORLD</span><span style="font-size:12.8px">} </span><span style="font-size:12.8px">and </span><span style="font-size:12.8px">\const</span><span style="font-size:12.8px">{</span><span style="font-size:12.8px">MPI</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">COMM</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">SELF</span><span style="font-size:12.8px">}</span><span style="font-size:12.8px"> may have unintended effects, as
changes to these </span><span style="font-size:12.8px">global
objects may affect all components of the application,
including libraries and tools."</span><br>
</div>
<div>
<div><br>
</div>
<div> George.</div>
<div><br>
</div>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Feb 9, 2016 at 8:02 PM, Jim
Dinan <span dir="ltr"><<a href="mailto:james.dinan@gmail.com" target="_blank">james.dinan@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div dir="ltr">We're calling the proposal "info assertions",
but the standard still refers to them as "hints".
<div><br>
</div>
<div>Reading the proposed change again, I think it might
be helpful (and more fair to tools) to say why info
could impact tools:</div>
<div><br>
</div>
<blockquote style="margin:0px 0px 0px 40px;border:none;padding:0px">
<div><span style="font-size:12.8px">Setting info hints
on the predefined communicators </span><span style="font-size:12.8px">\const</span><span style="font-size:12.8px">{</span><span style="font-size:12.8px">MPI</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">COMM</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">WORLD</span><span style="font-size:12.8px">} </span><span style="font-size:12.8px">and </span><span style="font-size:12.8px">\const</span><span style="font-size:12.8px">{</span><span style="font-size:12.8px">MPI</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">COMM</span><span style="font-size:12.8px">\_</span><span style="font-size:12.8px">SELF</span><span style="font-size:12.8px">}</span><span style="font-size:12.8px"> may have unintended
effects, as changes to these </span><span style="font-size:12.8px">global objects may affect
all components of the application, including
libraries. </span><span style="font-size:12.8px;background-color:rgb(255,255,0)">The
usage of some info hints may allow the MPI library
to change its behavior and, as a result, impact the
effectiveness of tools.</span><br>
</div>
<div><span style="font-size:12.8px;background-color:rgb(255,255,0)"><br>
</span></div>
</blockquote>
<div>
<div> ~Jim.</div>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">
<div>
<div>On Tue, Feb 9, 2016 at 12:38 PM,
Daniel Holmes <span dir="ltr"><<a href="mailto:dholmes@epcc.ed.ac.uk" target="_blank"></a><a href="mailto:dholmes@epcc.ed.ac.uk" target="_blank">dholmes@epcc.ed.ac.uk</a>></span>
wrote:<br>
</div>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div>
<div>
<div bgcolor="#FFFFFF" text="#000000"> Hi Jim,<br>
<br>
I like that change. On a side note: are we
really still calling them "info hints" in this
context rather than "info assertions"?<br>
<br>
Cheers,<br>
Dan.
<div>
<div><br>
<br>
<div>On 09/02/2016 15:51, Jim Dinan wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi All,
<div><br>
</div>
<div>I'm preparing the updated draft of
info assertions for a reading in
March. Where did we land on an advice
regarding tools? Do we want advice
(1) to users, that they info keys may
impact tools and/or (2) to tools that
they should check info?</div>
<div><br>
</div>
<div>For instance, we could extend the
current advice with the following
sentence:</div>
<div><span><br>
</span></div>
<div><span>Setting info hints on the
predefined communicators </span><span>\const</span><span>{</span><span>MPI</span><span>\_</span><span>COMM</span><span>\_</span><span>WORLD</span><span>} </span><span>and
</span><span>\const</span><span>{</span><span>MPI</span><span>\_</span><span>COMM</span><span>\_</span><span>SELF</span><span>}</span><span>
may have unintended effects, as
changes to these </span>global
objects may affect all components of
the application, including libraries.
<span style="background-color:rgb(255,255,0)">The
usage of info hints may also impact
the effectiveness of tools.</span></div>
<div><span style="background-color:rgb(255,255,0)"><br>
</span></div>
<div><span style="background-color:rgb(255,255,255)"> ~Jim.</span></div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Dec 18,
2015 at 5:24 AM, Marc-Andre Hermanns <span dir="ltr"><<a href="mailto:hermanns@jara.rwth-aachen.de" target="_blank"></a><a href="mailto:hermanns@jara.rwth-aachen.de" target="_blank">hermanns@jara.rwth-aachen.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><span>Hi
Jeff,<br>
<br>
> at the moment we don't
handle MPI_THREAD_MULTIPLE at all.
But we want<br>
> to get there ;-)<br>
><br>
><br>
> You should vote for
endpoints, as this may help you
out here,<br>
> particularly if users start
mapping endpoints 1:1 w/ threads.<br>
<br>
</span>That would certainly ease
things for us in these situations.<br>
Unfortunately endpoints force use to
adapt other infrastructure in our<br>
measurement system.<br>
<span><br>
> b) Creating a derived
datatype on the fly to add
tool-level data to<br>
> the original payload may
induce a large overhead in
practically<br>
> _every_ send &
receive operation and perturb the
measurement.<br>
><br>
><br>
> You should evaluate this
experimentally. I wrote a simple
test<br>
> (<a href="https://github.com/jeffhammond/BigMPI/blob/master/test/perf/typepiggy.c" rel="noreferrer" target="_blank">https://github.com/jeffhammond/BigMPI/blob/master/test/perf/typepiggy.c</a>)<br>
> and measured 1.5 us per call
of overhead to create a datatype.
That<br>
> is not significant except for
very small messages.<br>
<br>
</span>Thanks for the pointer. You
are right. I should evaluate this
further.<br>
1.5us does indeed seem tolerable. I
wonder how the influence of the<br>
derived datatype is on overall
messaging performance, though.<br>
<br>
This is also something I should
evaluate in the process.<br>
<span><br>
Cheers,<br>
Marc-Andre<br>
<br>
--<br>
Marc-Andre Hermanns<br>
Jülich Aachen Research Alliance,<br>
High Performance Computing
(JARA-HPC)<br>
Jülich Supercomputing Centre (JSC)<br>
<br>
Schinkelstrasse 2<br>
52062 Aachen<br>
Germany<br>
<br>
Phone: <a href="tel:%2B49%202461%2061%202509" value="+492461612509" target="_blank">+49 2461 61 2509</a>
| <a href="tel:%2B49%20241%2080%2024381" value="+492418024381" target="_blank">+49 241 80 24381</a><br>
Fax: <a href="tel:%2B49%202461%2080%206%2099753" value="+49246180699753" target="_blank">+49 2461 80 6
99753</a><br>
<a href="http://www.jara.org/jara-hpc" rel="noreferrer" target="_blank">www.jara.org/jara-hpc</a><br>
</span>email: <a href="mailto:hermanns@jara.rwth-aachen.de" target="_blank"></a><a href="mailto:hermanns@jara.rwth-aachen.de" target="_blank">hermanns@jara.rwth-aachen.de</a><br>
<br>
<br>
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<pre cols="72">--
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<pre cols="72">--
Dan Holmes
Applications Consultant in HPC Research
EPCC, The University of Edinburgh
James Clerk Maxwell Building
The Kings Buildings
Peter Guthrie Tait Road
Edinburgh
EH9 3FD
T: <a href="tel:%2B44%280%29131%20651%203465" value="+441316513465" target="_blank">+44(0)131 651 3465</a>
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