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<p class="MsoNormal"><span style="font-size:11.0pt">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Does PETSc has some automatic matrix sparsity detection algorithm available?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Something like: <a href="https://urldefense.us/v3/__https://docs.sciml.ai/NonlinearSolve/stable/basics/sparsity_detection/__;!!G_uCfscf7eWS!ccEx6zmuNrVADqtN50hO2N0k4Qs-A70nztAjMLu-JElnjhK5w84BpYC8CAINd6KihSxaS2rx_LgpqUVM49U$">
https://docs.sciml.ai/NonlinearSolve/stable/basics/sparsity_detection/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">The background is that I use finite differencing plus matrix coloring to (efficiently) get the Jacobian.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">For the matrix coloring part, I color the matrix based on mesh connectivity and variable dependencies, which is not bad, but just try to be lazy to even eliminating this part.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">A related but different question, how much does PETSc support automatic differentiation?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I see some old paper:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://ftp.mcs.anl.gov/pub/tech_reports/reports/P922.pdf">https://ftp.mcs.anl.gov/pub/tech_reports/reports/P922.pdf</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">and discussion in the roadmap:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://urldefense.us/v3/__https://petsc.org/release/community/roadmap/__;!!G_uCfscf7eWS!ccEx6zmuNrVADqtN50hO2N0k4Qs-A70nztAjMLu-JElnjhK5w84BpYC8CAINd6KihSxaS2rx_Lgpw6v6hKE$">https://petsc.org/release/community/roadmap/</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I am thinking that if AD works so I don’t even need to do finite differencing Jacobian, or have it as another option.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">-Ling<o:p></o:p></span></p>
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