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<p class="MsoNormal">Hi all<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am currently building a large software stack using Spack with PETSc 3.19 as part of the dependency library.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Spotted the following message during the build process<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:Consolas;color:#1F2328;border:none windowtext 1.0pt;padding:0cm;mso-fareast-language:EN-GB">Using default optimization C flags “-g -O”. You might consider manually setting optimal optimization flags
for your system with<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:Consolas;color:#1F2328;border:none windowtext 1.0pt;padding:0cm;mso-fareast-language:EN-GB">COPTFLAGS="optimization flags" see config/examples/arch-*-opt.py for examples</span><span style="font-size:9.0pt;font-family:Consolas;color:#1F2328;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Previously when we install PETSc manually, optimisation flags are enforced via configure script e.g.
<o:p></o:p></p>
<p class="MsoNormal">COPTFLAGS=”-g -O3 -march=native”<o:p></o:p></p>
<p class="MsoNormal">CXXOPTFLAGS=”-g -O3 -march=native” <o:p></o:p></p>
<p class="MsoNormal">…<o:p></o:p></p>
<p class="MsoNormal">(or “-g -O3 -xhost” for intel compiler)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Whilst spack spec syntax allows compiler parameters via cflags/cxxflags/fflags <o:p></o:p></p>
<p class="MsoNormal"><a href="https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/petsc/package.py#L400">https://github.com/spack/spack/blob/develop/var/spack/repos/builtin/packages/petsc/package.py</a><o:p></o:p></p>
<p class="MsoNormal">the requirement is not obvious, especially in a long build process.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The question is should optimisation be amended at spack recipe stage or should PETSc configure enforce some compiler optimisation (if –with-debugging=0 is set) ?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#00747B;mso-fareast-language:EN-GB">Dr Wei Liu<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#768693;mso-fareast-language:EN-GB">High Performance Computing
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#00747B;mso-fareast-language:EN-GB">To chat with me on Teams
</span><a href="https://teams.microsoft.com/l/chat/0/0?users=wei.liu@awe.co.uk"><span style="mso-fareast-language:EN-GB">click here</span></a><span style="color:#00747B;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#00747B;mso-fareast-language:EN-GB">T: +44 01189 856209<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#00747B;mso-fareast-language:EN-GB">M: </span>
<a href="mailto:wei.liu@awe.co.uk"><span style="mso-fareast-language:EN-GB">wei.liu@awe.co.uk</span></a><span style="color:#00747B;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#768693;mso-fareast-language:EN-GB">AWE Aldermaston,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#768693;mso-fareast-language:EN-GB">Reading, Berkshire, RG7 4PR<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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