[petsc-users] PCFIELDSPLIT with BoomerAMG preconditioning on a Schur Complement

[Jorti, Zakariae]

Hello,


I have a block matrix A,


[A_{00}   A_{01}]

[A_{10}   A_{11}] ,


and am trying to use PCFIELDSPLIT as a preconditioner on it. The preconditioner has this shape:


[inv(A_{00})       0     ]

[  0                -ksp(S)] ;


where S is the Schur Complement matrix:

S = A_{11} - A_{10} * inv(A_{00}) * A_{01},

that I get by calling:


MatGetSchurComplement(A, isrow0, iscol0, isrow1, iscol1, MAT_INITIAL_MATRIX, &S, MAT_SCHUR_COMPLEMENT_AINV_DIAG, MAT_IGNORE_MATRIX, NULL);


I would like to set BoomerAMG preconditioner for ksp(S). So, I am calling:



PCFieldSplitGetSubKSP(pc, &n, &subksp);

KSPSetOperators(subksp[1], S, S);

KSPGetPC(subksp[1], subpc);

PCSetType(subpc,"boomeramg");


but I end up getting the following error:


[0]PETSC ERROR: No support for this operation for this object type

[0]PETSC ERROR: Mat type schurcomplement

[0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.

[0]PETSC ERROR: Petsc Release Version 3.14.2, Dec 03, 2020

[0]PETSC ERROR: ./mimeticcurleuler2 on a arch-linux-c-debug named nid00140 by zjorti Tue Apr 20 12:23:34 2021

[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

[0]PETSC ERROR: #1 MatGetRow() line 561 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/interface/matrix.c

[0]PETSC ERROR: #2 MatConvert_Basic() line 53 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/utils/convert.c

[0]PETSC ERROR: #3 MatConvert() line 4254 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/mat/interface/matrix.c

[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

[0]PETSC ERROR: #5 PCSetUp() line 1009 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/interface/precon.c

[0]PETSC ERROR: #6 KSPSetUp() line 406 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c

[0]PETSC ERROR: #7 KSPSolve_Private() line 658 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c

[0]PETSC ERROR: #8 KSPSolve() line 889 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c

[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

[0]PETSC ERROR: #10 PCApply() line 444 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/pc/interface/precon.c

[0]PETSC ERROR: #11 KSP_PCApply() line 283 in /global/u1/z/zjorti/Software/petsc-3.14.2/include/petsc/private/kspimpl.h

[0]PETSC ERROR: #12 KSPInitialResidual() line 65 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itres.c

[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

[0]PETSC ERROR: #14 KSPSolve_Private() line 719 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c

[0]PETSC ERROR: #15 KSPSolve() line 889 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ksp/ksp/interface/itfunc.c

[0]PETSC ERROR: #16 SNESSolve_KSPONLY() line 51 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/snes/impls/ksponly/ksponly.c

[0]PETSC ERROR: #17 SNESSolve() line 4569 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/snes/interface/snes.c

[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

[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

[0]PETSC ERROR: #20 TSStep() line 3757 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/interface/ts.c

[0]PETSC ERROR: #21 TSSolve() line 4154 in /global/u1/z/zjorti/Software/petsc-3.14.2/src/ts/interface/ts.c


Am I doing something wrong here? How can I fix this?

Many thanks.


Best regards,


Zakariae Jorti



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