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Good point to raise, Alfredo. Tim – were you referring to this? Delete callback associated with communicators gets called when communicator is freed Consider finalize-delete-callback (this is what Alfredo is alluding to perhaps w. r. t datatype-attached-to-environment)</div>
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<p class="MsoNormal"><span style="font-size:11.0pt">Good point to raise, Alfredo.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Tim – were you referring to this?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Delete callback associated with communicators gets called when communicator is freed<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Consider finalize-delete-callback (this is what Alfredo is alluding to perhaps w.r.t datatype-attached-to-environment) – that seems to rely on MPI_COMM_SELF
callback (freeing comm-self triggers callback)<o:p></o:p></span></li></ul>
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<p class="MsoNormal"><span style="font-size:11.0pt">--<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Sayan Ghosh<br>
Computer Scientist<br>
Future Computing Technologies Group<br>
Pacific Northwest National Laboratory<br>
(509)-372-6323 • <a href="https://urldefense.us/v3/__https://sg0.github.io__;!!G_uCfscf7eWS!dDshRCeikLXOU8tk7BK4FrcfSKTeoJd4BHT-vBSD0yd_25QhX9DezifApWMlNnbtD1-LGkYDkcR-wbWl9odOPMR_YzXUmYnHr7UdKQ$"><span style="color:#467886">https://sg0.github.io</span></a><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">mpiwg-languages <mpiwg-languages-bounces@lists.mpi-forum.org> on behalf of Alfredo Correa via mpiwg-languages <mpiwg-languages@lists.mpi-forum.org><br>
<b>Date: </b>Friday, April 25, 2025 at 1:45</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-size:12.0pt;color:black">PM<br>
<b>To: </b>mpiwg-languages@lists.mpi-forum.org <mpiwg-languages@lists.mpi-forum.org>, tim.uhl@kit.edu <tim.uhl@kit.edu><br>
<b>Cc: </b>Alfredo Correa <alfredo.correa@gmail.com><br>
<b>Subject: </b>[mpiwg-languages] static datatypes lifetimes<o:p></o:p></span></p>
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<span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:black">Check twice before you click! This email originated from outside PNNL.</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span style="font-size:1.0pt;color:white">Hi Tim, the other day you mention that you played with attaching datatypes (specifically static data types) as keyvalues. This is very interesting. The first thing
I notice is that these datatypes will not be global, which is good. but it also<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">Hi Tim, the other day you mention that you played with attaching datatypes (specifically static data types) as keyvalues.
<br>
<br>
This is very interesting. The first thing I notice is that these datatypes will not be global, which is good. but it also means that they are attached to communicators, not the MPI environment. Am I correct?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">This would solve the problem of freeing datatypes on program exit.<br>
<br>
This is different from the idea of attaching it to environment that I was mentioning, but it is possible that attaching it to the communicator is actually a better idea. At the very least, because MPI has a mechanism to “attach” stuff to communicators, but
not to the environment.<o:p></o:p></span></p>
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