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Dear Thomas,
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<div>The McStas use of MCPL input in MPI settings is implemented in a relatively trivial way: </div>
<div><span class="Apple-tab-span" style="white-space:pre"></span>Every particle in the file is processed by every MPI process</div>
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<div>I therefore suspect that we could be looking at an I/O limitation from the filesystem - 1 vs. 10 vs. 64 processes wanting to read the same 24 Gb each from disk ‘in parallel’.</div>
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<div>- And I must admit we never benchmarked this part of the implementation wrt. performance…</div>
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<div>Thanks for letting us know - and let’s perhaps define a GItHub ticket on the topic where we can continue discussing / trying things out?</div>
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<div>Cheers,</div>
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<div>Peter</div>
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<div class="">On 7 Nov 2019, at 17.34, Huegle, Thomas <<a href="mailto:hueglet@ornl.gov" class="">hueglet@ornl.gov</a>> wrote:</div>
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Dear all,<o:p class=""></o:p></div>
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I am trying out using MCPL files as input into simulations right now:<o:p class=""></o:p></div>
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COMPONENT sourceMCPL = MCPL_input( filename="/data/source.mcpl" )<o:p class=""></o:p></div>
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AT (0, 0, 0) RELATIVE Origin<o:p class=""></o:p></div>
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When I run the simulation using simply “mcrun mcpltester.instr”, it takes about half an hour (the MCPL file in question is 24GB).<o:p class=""></o:p></div>
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However, when I try to use mpi (“mcrun -c --mpi=10 mcpltester.instr”), it takes something closer to 50 minutes. The problem seems to get worse (predicted run time for mpi=64: ~17 hours).<o:p class=""></o:p></div>
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Is there a way around it? Some special way of compiling perhaps?<o:p class=""></o:p></div>
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Thank you very much!<o:p class=""></o:p></div>
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Thomas<o:p class=""></o:p></div>
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<span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">mcstas-users
mailing list</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class="">
<a href="mailto:mcstas-users@mcstas.org" style="color: rgb(149, 79, 114); text-decoration: underline; font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">mcstas-users@mcstas.org</a><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class="">
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Peter Kjær Willendrup<br class="">
Forskningsingeniør, Specialkonsulent<br class="">
Næstformand for DTU Fysik LSU<br class="">
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DTU Physics<br class="">
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