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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I would say it depends on the situation. In most cases I would imagine the applications/tools would do the aggregation. And yes, in my example the processes
need to communicate to know the message pressure<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--Anh
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> mpiwg-tools [mailto:mpiwg-tools-bounces@lists.mpi-forum.org]
<b>On Behalf Of </b>Junchao Zhang<br>
<b>Sent:</b> Thursday, October 24, 2013 1:27 PM<br>
<b>To:</b> <mpiwg-tools@lists.mpi-forum.org><br>
<b>Subject:</b> Re: [mpiwg-tools] Using MPI_T<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi, Anh,<o:p></o:p></p>
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<p class="MsoNormal"> I think your example is to use feedback to do throttling. <o:p></o:p></p>
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<p class="MsoNormal"> A further question is: should we do it at application level (since you mentioned aggregation) or do it in MPI runtime?<o:p></o:p></p>
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<p class="MsoNormal"> The example also implies processes need to communicate to know pressure of each other.<o:p></o:p></p>
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<p class="MsoNormal"> Thanks.<o:p></o:p></p>
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<p class="MsoNormal"><br clear="all">
<o:p></o:p></p>
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<p class="MsoNormal">--Junchao Zhang<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
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<p class="MsoNormal">On Thu, Oct 24, 2013 at 2:40 PM, Anh Vo <<a href="mailto:Anh.Vo@microsoft.com" target="_blank">Anh.Vo@microsoft.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Junchao,</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">One example is monitoring the length of the unexpected message queues. Basically, when an MPI process
receives an incoming message from another MPI process and it has not posted a receive for such message yet, the message is typically copied into an unexpected receive queues. When the process posts a receive, it loops through the unexpected queue and sees
whether any of the messages in the queue would match with this receive. If the unexpected queue is too long, you would spend a lot of time looping through the queue. Extra memcpy operations are also needed for unexpected receive (vs the case where the message
arrives and there’s already a posted receive for it)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">By monitoring the length of the unexpected receive queue, the user can adjust the rate of message
flow. For example, if the other side processes messages fast enough, you can keep sending lots of small data (such as heart beat or piggyback), but in the case where the other side is slow processing messages (thus end up with high queue depth for unexpected
queue), it might be more beneficial to compress the message or aggregate them before sending</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--Anh</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><a name="141ebfb403c3b527__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span></a><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> mpiwg-tools [mailto:<a href="mailto:mpiwg-tools-bounces@lists.mpi-forum.org" target="_blank">mpiwg-tools-bounces@lists.mpi-forum.org</a>]
<b>On Behalf Of </b>Junchao Zhang<br>
<b>Sent:</b> Thursday, October 24, 2013 12:31 PM<br>
<b>To:</b> <<a href="mailto:mpiwg-tools@lists.mpi-forum.org" target="_blank">mpiwg-tools@lists.mpi-forum.org</a>><br>
<b>Subject:</b> [mpiwg-tools] Using MPI_T</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> The standard talks about the motivation of MPI_T as "MPI implementations often use internal variables to control their operation and performance. Understanding and manipulating
these variables can provide a more efficient execution environment or improve performance for many applications."<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> I could imagine that through performance variables, users can know MPI internal states during application execution. But how to use that to improve performance? What EXTRA advantages
does MPI_T bring? I don't get the idea.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> Can someone shed light on that?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> Thank you.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">--Junchao Zhang<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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