<div dir="ltr"><div dir="ltr">On Wed, Nov 16, 2022 at 9:07 PM Zhang, Hong 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="msg7487228530054485512">
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<span style="font-family:Menlo;font-size:12px;background-color:rgb(255,255,255);display:inline">Karhik,</span><br>
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<span style="font-family:Menlo;font-size:12px;background-color:rgb(255,255,255);display:inline">Can you find out the condition number of your matrix?</span></div>
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<span style="font-family:Menlo;font-size:12px;background-color:rgb(255,255,255);display:inline"></span></div></div></div></blockquote><div><br></div><div>Also, run using</div><div><br></div><div> -ksp_view -ksp_monitor_true_residual -ksp_converged_reason</div><div><br></div><div>and send the two outputs.</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="msg7487228530054485512"><div dir="ltr"><div style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:12pt;color:rgb(0,0,0);background-color:rgb(255,255,255)"><span style="font-family:Menlo;font-size:12px;background-color:rgb(255,255,255);display:inline">Hong</span></div>
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<div id="m_-7607706715142363214divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> petsc-users <<a href="mailto:petsc-users-bounces@mcs.anl.gov" target="_blank">petsc-users-bounces@mcs.anl.gov</a>> on behalf of Karthikeyan Chockalingam - STFC UKRI via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>><br>
<b>Sent:</b> Wednesday, November 16, 2022 6:04 PM<br>
<b>To:</b> <a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a> <<a href="mailto:petsc-users@mcs.anl.gov" target="_blank">petsc-users@mcs.anl.gov</a>><br>
<b>Subject:</b> [petsc-users] Different solution while running in parallel</font>
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<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> Hello,</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> I tried to solve a (FE discretized) Poisson equation using PCLU. For some reason I am getting different solutions while running the problem on one and two cores. I have attached the output file (out.txt) from both the
runs. I am printing A, b and x from both the runs – while A and b are the same but the solution seems is different.</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span>I am not sure what I doing wrong.</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span>Below is my matrix, vector, and solve setup.
</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span> <span style="color:rgb(57,0,160)">Mat</span> A;<span style="color:rgb(57,0,160)"></span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black"> </span><span style="font-size:9pt;font-family:Menlo;color:rgb(57,0,160)">Vec</span><span style="font-size:9pt;font-family:Menlo;color:black"> b, x;</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black"> </span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;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)">MatCreate</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">,
&A); </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);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;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)">MatSetType</span><span style="font-size:9pt;font-family:Menlo;color:black">(A,
</span><span style="font-size:9pt;font-family:Menlo;color:rgb(100,56,32)">MATMPIAIJ</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);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;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)">MatSetSizes</span><span style="font-size:9pt;font-family:Menlo;color:black">(A,
</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);
</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);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;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)">MatMPIAIJSetPreallocation</span><span style="font-size:9pt;font-family:Menlo;color:black">(A,d_nz,
</span><b><span style="font-size:9pt;font-family:Menlo;color:rgb(155,35,147)">NULL</span></b><span style="font-size:9pt;font-family:Menlo;color:black">, o_nz,
</span><b><span style="font-size:9pt;font-family:Menlo;color:rgb(155,35,147)">NULL</span></b><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);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:rgb(108,54,169)"> ierr = MatSetOption(A,MAT_SYMMETRIC,PETSC_TRUE);
</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:rgb(108,54,169)">(ierr);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;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">(A, &b, &x);
</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);</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span><span style="color:rgb(57,0,160)">KSP</span>
<span> </span>ksp;</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span><span style="color:rgb(57,0,160)">PC</span><span>
</span>pc;</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">
<span> </span>KSPCreate<span>(</span>PETSC_COMM_WORLD<span>, &ksp);</span></p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span><span style="color:rgb(108,54,169)">KSPSetOperators</span>(ksp, A, A);</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span>ierr = <span style="color:rgb(108,54,169)">
KSPSetType</span>(ksp,<span style="color:rgb(100,56,32)">KSPPREONLY</span>);<span style="color:rgb(100,56,32)">CHKERRQ</span>(ierr);</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span>ierr = <span style="color:rgb(108,54,169)">
KSPGetPC</span>(ksp,&pc);<span style="color:rgb(100,56,32)">CHKERRQ</span>(ierr);</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:black">
<span> </span>ierr = <span style="color:rgb(108,54,169)">
PCSetType</span>(pc,<span style="color:rgb(100,56,32)">PCLU</span>);<span style="color:rgb(100,56,32)">CHKERRQ</span>(ierr);</p>
<p style="margin:0cm;background:white;font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">
<span> </span><span>ierr = </span>
PCFactorSetMatSolverType<span>(pc,</span><span style="color:rgb(100,56,32)">MATSOLVERMUMPS</span><span>);</span><span style="color:rgb(100,56,32)">CHKERRQ</span><span>(ierr);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black"> </span><span style="font-size:9pt;font-family:Menlo;color:rgb(108,54,169)">KSPSolve</span><span style="font-size:9pt;font-family:Menlo;color:black">(ksp, b, x);</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black"> </span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black">Thank you for your help.</span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black"> </span></p>
<p style="margin:0cm;font-size:11pt;font-family:Calibri,sans-serif;background:white">
<span style="font-size:9pt;font-family:Menlo;color:black">Karhik.</span></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>