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<p class="MsoNormal"><span lang="FR" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hello Matthew,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="FR" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I was indeed wondering if there was a clean way to match a given set of options to a specific KSP instance. Does the following makes sense:<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Associate a given a KSP instance a unique string, e.g.
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">“toto”</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> and call
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">ksp_1.setOptionsPrefix(“toto”)</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Create an option database with corresponding prefix:
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">options = Options(“toto_ksp_”)</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Then a call to
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">ksp_1.setFromOptions()</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> will only consider entrees in the option database starting with
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">“toto”</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Alexandre.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="FR" style="font-size:11.0pt;font-family:"Calibri",sans-serif">De :</span></b><span lang="FR" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Matthew Knepley <knepley@gmail.com>
<br>
<b>Envoyé :</b> lundi 27 octobre 2025 11:27<br>
<b>À :</b> SCOTTO Alexandre <alexandre.scotto@irt-saintexupery.com><br>
<b>Cc :</b> petsc-users@mcs.anl.gov<br>
<b>Objet :</b> Re: [petsc-users] Options database in petsc4py<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Mon, Oct 27, 2025 at 10:24 AM SCOTTO Alexandre via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Dear PETSc Community,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">In my developments, I am managing possibly several KSP solvers with options handled by the Options database. During my tests, I encountered the following behavior:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b>Code</b>:<o:p></o:p></p>
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<span style="font-family:"Courier New";background:silver">options = PETSc.Options("ksp_")</span><o:p></o:p></p>
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<span style="font-family:"Courier New";background:silver">options.setValue("atol", 7e-8)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">options.view()</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">options.clear()</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">options.view()</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b>Output</b>:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">#PETSc Option Table entries:</span><o:p></o:p></p>
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<span lang="FR" style="font-family:"Courier New";background:silver">-ksp_atol 7e-08 # (source: code)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">#End of PETSc Option Table entries</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">#PETSc Option Table entries:</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">-ksp_atol 7e-08 # (source: code)</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New";background:silver">#End of PETSc Option Table entries</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:36.0pt">
<span style="font-family:"Courier New""> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">It seems that the
<span style="font-family:"Courier New";background:silver">clear()</span> method does not really clear the Option database. To ensure that the several KSP I deal with are set with their own options (without getting options from a KSP previously set), the only
way I found was to explicitly call the <span style="font-family:"Courier New";background:silver">
delValue()</span> method for all the option keys passed:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="m-5483869375695487431msolistparagraph">1.<span style="font-size:7.0pt">
</span>Iterate over a dictionary of options and use <span style="font-family:"Courier New";background:silver">
setValue(name, value)</span><o:p></o:p></p>
<p class="m-5483869375695487431msolistparagraph">2.<span style="font-size:7.0pt">
</span>Set the KSP with option database: <span style="font-family:"Courier New";background:silver">
KSP.setFromOptions()</span><o:p></o:p></p>
<p class="m-5483869375695487431msolistparagraph">3.<span style="font-size:7.0pt">
</span>Iterate over a the keys of the dictionary and <span style="font-family:"Courier New"">
use <span style="background:silver">delValue(name)</span></span> to effectively clear the option database.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Does it seem normal to you, is there something I am missing out?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">That for pointing out this bug.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">However, I don't think I would manage options this way. We normally give each separate solver a new _prefix_, meaning a string that prefaces all its options. That way they do not collide.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> Thanks,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> Matt<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Regards,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Alexandre Scotto.<o:p></o:p></p>
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<p class="MsoNormal"><br clear="all">
<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span class="gmailsignatureprefix">-- </span><o:p></o:p></p>
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<p class="MsoNormal">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><a href="https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!ZnPxnrdflWTbGbGUEH1FqwWm8qDvjVXbO9Vcz0i-G4kvOUAXnvdAeosPUQrtGbXE74bfCgrSlkSnKeAt0Pd0lPTS4gzeowrsYHPXgj5rjg$" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><o:p></o:p></p>
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