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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>
<br>
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>
<br>
Cheers,<br>
Dan.<br>
<br>
<div class="moz-cite-prefix">On 09/02/2016 22:36, George Bosilca
wrote:<br>
</div>
<blockquote
cite="mid:CAMJJpkVOwOmVGQ8MqhZvhbK-655sUUBsMmmvSgro4EWtNExTAw@mail.gmail.com"
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 moz-do-not-send="true"
href="mailto:james.dinan@gmail.com" target="_blank">james.dinan@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc 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 class="h5">On Tue, Feb 9, 2016 at 12:38 PM,
Daniel Holmes <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:dholmes@epcc.ed.ac.uk"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:dholmes@epcc.ed.ac.uk">dholmes@epcc.ed.ac.uk</a></a>></span>
wrote:<br>
</div>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div class="h5">
<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
moz-do-not-send="true"
href="mailto:hermanns@jara.rwth-aachen.de"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:hermanns@jara.rwth-aachen.de">hermanns@jara.rwth-aachen.de</a></a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
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 moz-do-not-send="true"
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>
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Dan Holmes
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