<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: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 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: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 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: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 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>
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52062 Aachen<br>
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<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>
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<br>
<br>
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