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<p class="MsoNormal"><span style="font-size:11.0pt">Thank you both Jed and Stefano.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Then, somehow, I may have introduced inconsistence in my code, because I expected they have exactly the same behavior.<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">-Ling<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">Stefano Zampini <stefano.zampini@gmail.com><br>
<b>Date: </b>Friday, August 22, 2025 at 4:42</span><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:black"> </span><span style="font-size:12.0pt;color:black">PM<br>
<b>To: </b>Zou, Ling <lzou@anl.gov><br>
<b>Cc: </b>PETSc <petsc-users@mcs.anl.gov><br>
<b>Subject: </b>Re: [petsc-users] Understanding 'snes' object<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span style="font-size:1.0pt;color:white">Il giorno sab 23 ago 2025 alle ore 00:</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">25
Zou, Ling via petsc-users <petsc-users@</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">mcs.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">anl.</span><span style="font-size:1.0pt;font-family:"Arial",sans-serif;color:white"> </span><span style="font-size:1.0pt;color:white">gov>
ha scritto: Hi all, Can someone please help me understand the output of the following two outputs using ‘-snes_view’? Option 1: SNES Object: 1<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">Il giorno sab 23 ago 2025 alle ore 00:25 Zou, Ling via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> ha scritto:<o:p></o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Hi all,</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Can someone please help me understand the output of the following two outputs using ‘-snes_view’?</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Option 1:</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812s1">SNES Object: 1 MPI process</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">type: newtonls</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">maximum iterations=15, maximum function evaluations=10000</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">tolerances: relative=1e-08, absolute=1e-50, solution=1e-08</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">total number of linear solver iterations=5</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">total number of function evaluations=14</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">norm schedule ALWAYS</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space"><span style="color:#00B050">
</span></span><span class="m-7958132393732476812s1"><span style="color:#00B050">Jacobian is built using finite differences with coloring</span></span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Option 2:</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812s1">SNES Object: 1 MPI process</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">type: newtonls</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">maximum iterations=50, maximum function evaluations=10000</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">tolerances: relative=1e-08, absolute=1e-50, solution=1e-08</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">total number of linear solver iterations=8</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">total number of function evaluations=17</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space">
</span><span class="m-7958132393732476812s1">norm schedule ALWAYS</span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space"><span style="color:#00B050">
</span></span><span class="m-7958132393732476812s1"><span style="color:#00B050">Jacobian is applied matrix-free with differencing</span></span><o:p></o:p></p>
<p class="m-7958132393732476812p1"><span class="m-7958132393732476812apple-converted-space"><span style="color:#00B050">
</span></span><span class="m-7958132393732476812s1"><span style="color:#00B050">Preconditioning Jacobian is built using finite differences with coloring</span></span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Does it mean that</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<li class="m-7958132393732476812msolistparagraph" style="mso-list:l0 level1 lfo1">
<span style="font-size:11.0pt">Option 1 uses Newton’s method, such that J du = b is solved with J being explicitly constructed?</span><o:p></o:p></li></ul>
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<p class="MsoNormal"><span style="font-size:12.0pt">yes<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"> <o:p></o:p></span></p>
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<o:p> </o:p></li><li class="m-7958132393732476812msolistparagraph" style="mso-list:l2 level1 lfo2">
<span style="font-size:11.0pt">Option 2 uses matrix free method, such that J du = b is solved with J v ~ (F(u + dv) – F(u)) / h when needed, e.g., in a Krylov method.</span><o:p></o:p></li></ul>
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<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">yes, and the preconditioner is constructed using an explicitly constructed Jacobian matrix<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"> <o:p></o:p></span></p>
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<o:p> </o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">Thanks,</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt">-Ling</span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt"> </span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"><br clear="all">
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span class="gmailsignatureprefix"><span style="font-size:12.0pt">--
</span></span><span style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt">Stefano<o:p></o:p></span></p>
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