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<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have so far solved scalar field problems using finite elements on a given (<b>unstructured</b>) mesh. I made use of
<span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">MATMPIAIJ</span> to create matrixes,
<span class="s1">MatCreateVecs</span>(<span class="s2">A</span>, &<span class="s2">b</span>, &<span class="s2">x</span>) to create vectors, and
<span style="color:#6C36A9;mso-ligatures:none;mso-fareast-language:EN-GB">MatZeroRowsColumnsIS
</span>to set boundary conditions.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">Now, I would like to solve a coupled system of equations for the quantities u1 and u2 on the
</span><span style="color:black">(<b>unstructured</b>) </span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">mesh. I.e., the matrix should get the double number of rows and columns,
<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">A = [A00 A01
<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"> A10 A11]<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">the vectors contain twice the number of entries (e.g. first all u1s and then all u2s). I would like to be sure that the entries of u1 and u2,
which are associated with the same element are located on the same processor.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">Is a pre-defined structure already available within PETSc to enlarge such a single equation to store the entries of coupled equations?<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-\Delta u_1+c_{11} u_1+c_{12} u_2=f_1<o:p></o:p></p>
<p class="MsoNormal">-\Delta u_2+c_{21} u_1+c_{22} u_2=f_2<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="background:white"><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">Would I still be able to use
</span><span style="color:#6C36A9;mso-ligatures:none;mso-fareast-language:EN-GB">MatZeroRowsColumnsIS
</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">u1 and u2 independently to enforce boundary conditions?
</span><span style="color:#6C36A9;mso-ligatures:none;mso-fareast-language:EN-GB">MatZeroRowsColumnsIS</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">(</span><span style="color:#326D74;mso-ligatures:none;mso-fareast-language:EN-GB">A</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">,
</span><span style="color:#326D74;mso-ligatures:none;mso-fareast-language:EN-GB">is</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">,
</span><span style="color:#1C00CF;mso-ligatures:none;mso-fareast-language:EN-GB">1</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">,
</span><span style="color:#326D74;mso-ligatures:none;mso-fareast-language:EN-GB">x</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">,
</span><span style="color:#326D74;mso-ligatures:none;mso-fareast-language:EN-GB">b</span><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">);<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I don’t know where to begin. I have so far only been exposed to using
<span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">MATMPIAIJ and MatSetValues to create and assign values to matrix entries respectively.
</span>I would be grateful if you could provide the stepwise guide.</p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Kind regards,</p>
<p class="MsoNormal">Karthik.</p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:EN-GB">-- <o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#2D2D62;mso-ligatures:none;mso-fareast-language:EN-GB">Karthik Chockalingam, Ph.D.<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none;mso-fareast-language:EN-GB">Senior Research Software Engineer</span><span style="font-size:10.5pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none;mso-fareast-language:EN-GB">High Performance Systems Engineering Group</span><span style="font-size:10.5pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:black;mso-ligatures:none;mso-fareast-language:EN-GB">Hartree Centre | Science and Technology Facilities Council</span><span style="font-size:10.5pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#212121;mso-ligatures:none;mso-fareast-language:EN-GB"><a href="mailto:karthikeyan.chockalingam@stfc.ac.uk">karthikeyan.chockalingam@stfc.ac.uk</a></span><span style="color:#212121;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"> </span><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#414141;mso-ligatures:none;mso-fareast-language:EN-GB"> </span><span style="color:#212121;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.5pt;font-family:"Arial",sans-serif;color:#414141;mso-ligatures:none;mso-fareast-language:EN-GB"> </span></b><span style="font-size:12.0pt;font-family:"Times New Roman",serif;color:#1F497D;mso-ligatures:none;mso-fareast-language:EN-GB"><img border="0" width="254" height="116" style="width:2.6458in;height:1.2083in" id="Picture_x0020_1" src="file:////Users/karthikeyan.chockalingam/Library/Containers/com.microsoft.Outlook/Data/Library/Caches/Signatures/signature_1995467923" alt="signature_3970890138"></span><span style="color:#212121;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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