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<p>Hello,</p>
<p><br>
</p>
<p>I have a block matrix A,</p>
<p><br>
</p>
<p>[A_{00} A_{01}]</p>
<p>[A_{10} A_{11}] , </p>
<p><br>
</p>
<p>and <span style="font-size: 12pt;">a</span><span style="font-size: 12pt;">m trying to use PCFIELDSPLIT as a preconditioner on</span><span style="font-size: 12pt;"> it. The preconditioner has this shape: </span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p>[inv(A_{00}) 0 ]</p>
<p>[ 0 -ksp(S)] ;</p>
<p><br>
</p>
<p>where S is the Schur Complement matrix: </p>
<p>S = <span style="font-size: 12pt;">A_{11} - </span><span style="font-size: 12pt;">A_{10} * inv(</span><span style="font-size: 12pt;">A_{00}</span><span style="font-size: 12pt;">) * </span><span style="font-size: 12pt;">A_{01},</span></p>
<p><span style="font-size: 12pt;">that I get by calling: </span></p>
<p><br>
</p>
<p>MatGetSchurComplement(A, isrow0, iscol0, isrow1, iscol1, MAT_INITIAL_MATRIX, &S, MAT_SCHUR_COMPLEMENT_AINV_DIAG, MAT_IGNORE_MATRIX, NULL);</p>
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<p><span style="font-size: 12pt;">I would like to set BoomerAMG preconditioner for </span>ksp(S). So, I am calling:</p>
<p> </p>
<p>PCFieldSplitGetSubKSP(pc, &n, &subksp);</p>
<p>KSPSetOperators(subksp[1], S, S);</p>
<p>KSPGetPC(<span style="font-size: 12pt;">subksp[1],</span><span style="font-size: 12pt;"> subpc</span><span style="font-size: 12pt;">);</span></p>
<p><span style="font-size: 12pt;">PCSetType(subpc,"boomeramg");</span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;">but I end up getting the following error:</span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p>[0]PETSC ERROR: No support for this operation for this object type</p>
<p>[0]PETSC ERROR: Mat type schurcomplement</p>
<p>[0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.</p>
<p>[0]PETSC ERROR: Petsc Release Version 3.14.2, Dec 03, 2020 </p>
<p>[0]PETSC ERROR: ./mimeticcurleuler2 on a arch-linux-c-debug named nid00140 by zjorti Tue Apr 20 12:23:34 2021</p>
<p>[0]PETSC ERROR: Configure options CC=cc CXX=CC FC=ftn COPTFLAGS=-g CXXOPTFLAGS=-g FOPTFLAGS=-g --download-hypre --with-debugging=1 --with-cxx-dialect=C++11</p>
<p>[0]PETSC ERROR: #1 MatGetRow() line 561 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/interface/matrix.c</p>
<p>[0]PETSC ERROR: #2 MatConvert_Basic() line 53 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/utils/convert.c</p>
<p>[0]PETSC ERROR: #3 MatConvert() line 4254 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/interface/matrix.c</p>
<p>[0]PETSC ERROR: #4 PCSetUp_HYPRE() line 231 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/impls/hypre/hypre.c</p>
<p>[0]PETSC ERROR: #5 PCSetUp() line 1009 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/interface/precon.c</p>
<p>[0]PETSC ERROR: #6 KSPSetUp() line 406 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c</p>
<p>[0]PETSC ERROR: #7 KSPSolve_Private() line 658 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c</p>
<p>[0]PETSC ERROR: #8 KSPSolve() line 889 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c</p>
<p>[0]PETSC ERROR: #9 PCApply_FieldSplit_Schur() line 1133 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/impls/fieldsplit/fieldsplit.c</p>
<p>[0]PETSC ERROR: #10 PCApply() line 444 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/interface/precon.c</p>
<p>[0]PETSC ERROR: #11 KSP_PCApply() line 283 in /global/u1/z/zjorti/Software/petsc-3.14.2/include/petsc/private/kspimpl.h</p>
<p>[0]PETSC ERROR: #12 KSPInitialResidual() line 65 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itres.c</p>
<p>[0]PETSC ERROR: #13 KSPSolve_GMRES() line 245 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/impls/gmres/gmres.c</p>
<p>[0]PETSC ERROR: #14 KSPSolve_Private() line 719 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c</p>
<p>[0]PETSC ERROR: #15 KSPSolve() line 889 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c</p>
<p>[0]PETSC ERROR: #16 SNESSolve_KSPONLY() line 51 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/snes/impls/ksponly/ksponly.c</p>
<p>[0]PETSC ERROR: #17 SNESSolve() line 4569 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/snes/interface/snes.c</p>
<p>[0]PETSC ERROR: #18 TSTheta_SNESSolve() line 185 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/impls/implicit/theta/theta.c</p>
<p>[0]PETSC ERROR: #19 TSStep_Theta() line 223 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/impls/implicit/theta/theta.c</p>
<p>[0]PETSC ERROR: #20 TSStep() line 3757 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/interface/ts.c</p>
<p>[0]PETSC ERROR: #21 TSSolve() line 4154 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/interface/ts.c</p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;">Am I doing something </span>wrong here? How can I fix this?</p>
<p>Many thanks.</p>
<p><br>
</p>
<p>Best regards,</p>
<p><br>
</p>
<p>Zakariae Jorti</p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;"></span><span style="font-size: 12pt;"> </span></p>
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