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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Beowulf <beowulf-bounces@beowulf.org> on behalf of Oddo Da <oddodaoddo@gmail.com><br>
<b>Date: </b>Wednesday, October 14, 2020 at 11:09 AM<br>
<b>To: </b>Michael Di Domenico <mdidomenico4@gmail.com><br>
<b>Cc: </b>"beowulf@beowulf.org" <beowulf@beowulf.org><br>
<b>Subject: </b>[EXTERNAL] Re: [Beowulf] ***UNCHECKED*** Re: Spark, Julia, OpenMPI etc. - all in one place<o:p></o:p></span></p>
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<p class="MsoNormal">On Wed, Oct 14, 2020 at 1:24 PM Michael Di Domenico <<a href="mailto:mdidomenico4@gmail.com">mdidomenico4@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:11.55pt">On Wed, Oct 14, 2020 at 11:53 AM Oddo Da <<a href="mailto:oddodaoddo@gmail.com" target="_blank">oddodaoddo@gmail.com</a>> wrote:<br>
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<p class="MsoNormal">i'll agree that in some respects software engineering has gotten<br>
better in the last 20yrs, but it's subjective. there are a lot of<br>
things that have gotten better and there are a lot of things that are<br>
much worse. but i'm not sure you can apply that statement to HPC.<br>
HPC code doesn't churn like business code or even more volatile cloud<br>
code. HPC code is usually written to solve something specific and<br>
gets incremental updates over time. usually that something specific<br>
hasn't changed the last 20yrs (think physics/chemistry) the models we<br>
use to describe or solve the problems likely have, but the underlying<br>
code is probably basically the same with tweaks along the way to fit<br>
the new model.<o:p></o:p></p>
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<p class="MsoNormal">I disagree. I think yes, there is old code that does not churn but there are always new people/grad students coming into the field. They too are being pointed in the same direction of how to do things, which is what we are discussing here
;-)<o:p></o:p></p>
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<p class="MsoNormal">Yes, there are new people coming in. But they’re not developing new modeling codes from scratch – they’re typically “improving” the existing codes. And as Michael pointed out, there’s significant resistance to change when you’ve got
a code base that is known, debugged, and has known warts. Big changes occur when a modeling paradigm shift occurs. And those are not real common.<o:p></o:p></p>
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<p class="MsoNormal">an evolution to MPI. but it goes back to technical debt. to re-write<br>
something in chapel is non-trivial and may not be worth the time.<br>
writing something new and choosing chapel is really left up to the<br>
developer. i have some chapel users here and there, but they're a<br>
minority. and since chapel is largely only found on cray machines its<br>
exposure is low<o:p></o:p></p>
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<p class="MsoNormal" style="border:none;padding:0in">It seems that in your world nothing new ever gets written? You are talking only about re-writes ;).<o:p></o:p></p>
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<p class="MsoNormal">For many HPC science applications this is true – Physics models change very slowly. Once you have a gridded finite element model, it “just works” and there’s not huge demand for new modeling approaches.<o:p></o:p></p>
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<p class="MsoNormal">Changes in language usage usually occur because of a technical problem with the existing code that means it just cannot be modified. More than one ambitious person has said “let’s re-do program X from Fortran to C++ or Java or Ada or Python”
and found it a bigger challenge than expected. There is a definite preference for the devil you know.<o:p></o:p></p>
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