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<p class="MsoNormal">It looks though the LLVM OpenMP runtime has two different stack size for x86 (4096kb) and power (1024kb), so I thought that this is not implementation related but maybe architecture dependent?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Anyway, makes sense to set the OMP_STACKSIZE.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.<o:p></o:p></p>
<p class="MsoNormal">Simone<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> Cownie, James H <james.h.cownie@intel.com> <br>
<b>Sent:</b> Monday, October 8, 2018 5:05 PM<br>
<b>To:</b> Simone Atzeni <satzeni@nvidia.com><br>
<b>Cc:</b> openmp-dev@lists.llvm.org<br>
<b>Subject:</b> RE: Default value for OpenMP thread stacksize<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D">I do not know what the default OpenMP stack size is on PPC, but the rest of your logic seems sound, and setting
</span><span lang="EN-GB" style="font-size:10.0pt;font-family:"Lucida Console";color:#1F497D">OMP_STACKSIZE</span><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D"> seems entirely reasonable.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D">The standard says that the default stack size is “implementation defined”, so it is entirely reasonable that different implementations have different
default values.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D">-- Jim<br>
<br>
Jim Cownie <<a href="mailto:james.h.cownie@intel.com">james.h.cownie@intel.com</a>><br>
CVCG/DPD/TCAR (Technical Computing, Analyzers, and Runtimes)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D">Tel: +44 117 9071438</span><span lang="EN-GB" style="color:#1F497D"><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Verdana",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><a name="_____replyseparator"></a><b>From:</b> Openmp-dev [<a href="mailto:openmp-dev-bounces@lists.llvm.org">mailto:openmp-dev-bounces@lists.llvm.org</a>]
<b>On Behalf Of </b>Simone Atzeni via Openmp-dev<br>
<b>Sent:</b> Monday, October 8, 2018 3:58 PM<br>
<b>To:</b> <a href="mailto:openmp-dev@lists.llvm.org">openmp-dev@lists.llvm.org</a><br>
<b>Subject:</b> [Openmp-dev] Default value for OpenMP thread stacksize<o:p></o:p></p>
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<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal">HI all,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">What’s the default size for the stack of the OpenMP threads in x86 and and ppc64 in the OpenMP runtime?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have a Fortran program which allocates more than a 1MB on the stack for each thread. On x86 runs correctly, but on ppc64 it seg faults.<o:p></o:p></p>
<p class="MsoNormal">I am seeing that each thread in x86 has a stacksize of 4096kb while on ppc64 is 1024kb.
<o:p></o:p></p>
<p class="MsoNormal">If I increase the stacksize with OMP_STACKSIZE the program runs correctly also on Power, but it fails if I only set “ulimit -s unlimited”, which make sense since ulimit should only change the stacksize for the main thread but not for the
other threads.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is this the expected behavior and the correct solution is to set OMP_STACKSIZE?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks.<o:p></o:p></p>
<p class="MsoNormal">Simone<o:p></o:p></p>
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