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<body class='hmmessage'><div dir='ltr'>Dear PETSc users,<br><br>This is Guoyi Ke, a graduate student of Texas Tech University. I have a 2D Navier Stokes problem that has block matrices: J=[F B^T; B 0]. I use Schur complement preconditioner for block J. The code was set as:<br><br> PCFieldSplitSetType( pc, PC_COMPOSITE_SCHUR );<br> PCFieldSplitSetSchurFactType(pc, PC_FIELDSPLIT_SCHUR_FACT_LOWER);<br> PCFieldSplitSetSchurPre(pc,PC_FIELDSPLIT_SCHUR_PRE_SELFP,NULL);<br><br>For both velocity block (fieldsplit: 0) and pressure block (fieldsplit: 1) , we set the KSP as KSPPREONLY and PC as PCILU. For this case, it works fine for us. <br>However, in order to use LSC we change the code as:<br><br> PCFieldSplitSetType( pc, PC_COMPOSITE_SCHUR );<br> PCFieldSplitSetSchurFactType(pc, PC_FIELDSPLIT_SCHUR_FACT_LOWER);<br> PCFieldSplitSetSchurPre(pc,<b>PC_FIELDSPLIT_SCHUR_PRE_SELF</b>,NULL);<br><br>We keep the same setup for velocity block (fieldsplit: 0) as above. For pressure block (fieldsplit: 1), we set the KSP as KSPGMRES and PC as PCLSU. I got the following errors:<br><br><!--[if gte mso 9]><xml>
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<p class="MsoNormal">[0]PETSC ERROR: --------------------- Error Message
--------------------------------------------------------------</p>
<p class="MsoNormal">[0]PETSC ERROR: Object is in wrong state</p>
<p class="MsoNormal">[0]PETSC ERROR: Matrix is missing diagonal entry 0</p>
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<![endif]--><br><br>Any suggestion and help will be highly appreciated. Thank you so much!<br><br>Best,<br>Guoyi <br><br><br><br> </div></body>
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