<div dir="ltr"><div dir="ltr">On Fri, Dec 2, 2022 at 7:48 AM Karthikeyan Chockalingam - STFC UKRI via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-2169580534702785644">
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<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><span style="font-size:10pt">Hello,</span></span><span class="m_-5165276704129641091s1"><u></u><u></u></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><span style="font-size:10pt"><u></u> <u></u></span></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><span style="font-size:10pt">I have system matrix which is symmetric and thought I could make use of
</span></span><span style="font-size:9pt;color:rgb(108,54,169)">MatCreateSBAIJ. </span>
<span class="m_-5165276704129641091s1"><span style="font-size:10pt">I don’t understand how to set the blocksize bs. I believe it has taken into account, when having multiple components/dofs per node.<u></u><u></u></span></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><u></u> <u></u></span></p>
<p class="m_-5165276704129641091p1" style="margin-left:72pt">
<u></u><span class="m_-5165276704129641091s1"><span style="font-size:10pt"><span>(i)<span style="font:7pt "Times New Roman"">
</span></span></span></span><u></u><span class="m_-5165276704129641091s1"><span style="font-size:10pt">Currently, I have only one scalar field to solve so I set bs = 1 as below. Is it correct?<u></u><u></u></span></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><u></u> <u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:9pt;font-family:Menlo;color:black"> ierr =
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">MatCreateSBAIJ</span><span style="font-size:9pt;font-family:Menlo;color:black">(</span><span style="font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">PETSC_COMM_WORLD</span><span style="font-size:9pt;font-family:Menlo;color:black">,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(28,0,207)">1</span><span style="font-size:9pt;font-family:Menlo;color:black">,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">PETSC_DECIDE</span><span style="font-size:9pt;font-family:Menlo;color:black">,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">PETSC_DECIDE</span><span style="font-size:9pt;font-family:Menlo;color:black">, N, N, d_nz,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">PETSC_NULL</span><span style="font-size:9pt;font-family:Menlo;color:black">, o_nz,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">PETSC_NULL</span><span style="font-size:9pt;font-family:Menlo;color:black">, &</span><span style="font-size:9pt;font-family:Menlo;color:rgb(50,109,116)">A</span><span style="font-size:9pt;font-family:Menlo;color:black">);
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">CHKERRQ</span><span style="font-size:9pt;font-family:Menlo;color:black">(ierr);<u></u><u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:9pt;font-family:Menlo;color:black"><u></u> <u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:9pt;font-family:Menlo;color:black"> ierr =
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">MatCreateVecs</span><span style="font-size:9pt;font-family:Menlo;color:black">(</span><span style="font-size:9pt;font-family:Menlo;color:rgb(50,109,116)">A</span><span style="font-size:9pt;font-family:Menlo;color:black">,
&</span><span style="font-size:9pt;font-family:Menlo;color:rgb(50,109,116)">right</span><span style="font-size:9pt;font-family:Menlo;color:black">, &</span><span style="font-size:9pt;font-family:Menlo;color:rgb(50,109,116)">left</span><span style="font-size:9pt;font-family:Menlo;color:black">);</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">CHKERRQ</span><span style="font-size:9pt;font-family:Menlo;color:black">(ierr);<u></u><u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:9pt;font-family:Menlo;color:black"><u></u> <u></u></span></p>
<p class="MsoNormal" style="background:white"><span style="font-size:9pt;font-family:Menlo;color:black"><u></u> <u></u></span></p>
<p class="m_-5165276704129641091MsoListParagraph" style="margin-left:72pt;background:white">
<u></u><span style="font-size:9pt;font-family:Menlo;color:black"><span>(ii)<span style="font:7pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:9pt;font-family:Menlo;color:black">If you multiple components/dofs per node, say 2, is the then block size = 2?<u></u><u></u></span></p>
<p class="m_-5165276704129641091MsoListParagraph" style="margin-left:72pt;background:white"><span style="font-size:9pt;font-family:Menlo;color:black"><u></u> <u></u></span></p>
<p class="m_-5165276704129641091MsoListParagraph" style="margin-left:72pt;background:white">
<u></u><span style="font-size:9pt;font-family:Menlo;color:black"><span>(iii)<span style="font:7pt "Times New Roman"">
</span></span></span><u></u><span style="font-size:9pt;font-family:Menlo;color:black">To apply homogenous Dirichlet boundary condition, I make use of MatZeroRowsColumns. It works in serial but while applying in parallel the following
error is thrown, <u></u><u></u></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><u></u> <u></u></span></p>
<p class="m_-5165276704129641091p1" style="text-indent:36pt"><span class="m_-5165276704129641091s1"><span style="font-size:10pt">[0]PETSC ERROR: No method zerorowscolumns for Mat of type mpisbaij<u></u><u></u></span></span></p>
<p class="m_-5165276704129641091p1" style="text-indent:36pt"><span class="m_-5165276704129641091s1"><span style="font-size:10pt"><u></u> <u></u></span></span></p>
<p class="m_-5165276704129641091p1" style="text-indent:36pt"><span class="m_-5165276704129641091s1"><span style="font-size:10pt"> How do I fix it?<u></u><u></u></span></span></p>
<p class="m_-5165276704129641091p1"><span class="m_-5165276704129641091s1"><span style="font-size:10pt"><u></u> <u></u></span></span></p>
<p class="m_-5165276704129641091MsoListParagraph" style="margin-left:72pt">
<u></u><span>(iv)<span style="font:7pt "Times New Roman"">
</span></span><u></u><span style="font-size:9pt;font-family:Menlo;color:black">Is there performance again, when using
</span><span style="font-size:9pt;color:rgb(108,54,169)">MatCreateSBAIJ </span><span style="font-size:9pt;font-family:Menlo;color:black">for large symmetric system matrix? I read there is more communication involved.</span></p></div></div></div></blockquote><div>For block size 1, there is no improvement. Even for 2 I would say it is small. The SBAIJ matrix will do the same number of flops</div><div>and use about the same bandwidth, but it will save on storage. Unless storage is a big deal for you, I would use AIJ, get everything</div><div>working, and profile to see how important various operations are.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="msg-2169580534702785644"><div lang="EN-GB" style="overflow-wrap: break-word;"><div class="m_-5165276704129641091WordSection1">
<p class="MsoNormal">Best,</p>
<p class="MsoNormal">Karthik.</p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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</div></blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>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</div><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div>