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<p>Hi all,</p>
<p>I am trying to solve linear systems arising from isogeometric
discretization (similar to FEM) of the Navier-Stokes equations in
parallel using PETSc. The linear systems are of saddle-point type,
so I would like to use the PCFIELDSPLIT preconditioner with the
-pc_fieldsplit_detect_saddle_point option, Schur complement
factorization and the LSC Schur complement preconditioner. I do
not provide any user-defined operators for PCLSC in my codes (at
least for now). </p>
<p>I store the matrix as a MATNEST consisting of 4 blocks (F for
velocity-velocity part, Bt for velocity-pressure part, B for
pressure-velocity part and NULL for pressure-pressure part). It is
also convenient for me to store the blocks F, Bt and B as another
MATNEST consisting of blocks corresponding to individual velocity
components. <br>
</p>
<p><br>
However, in this setting, I get the following error message:<br>
</p>
<p><i>[0]PETSC ERROR: Petsc has generated inconsistent data<br>
[0]PETSC ERROR: Unspecified symbolic phase for product AB with A
nest, B nest. Call MatProductSetFromOptions() first<br>
[0]PETSC ERROR: See <a class="moz-txt-link-freetext" href="https://petsc.org/release/faq/">https://petsc.org/release/faq/</a> for trouble
shooting.<br>
[0]PETSC ERROR: Petsc Release Version 3.20.4, unknown <br>
[0]PETSC ERROR:
/home/hhornik/gismo/build-petsc-mpi/RelWithDebInfo/bin/gsINSSolverPETScTest
on a arch-debug named ThinkPad-T14 by hhornik Thu Feb 8
11:04:17 2024<br>
[0]PETSC ERROR: Configure options PETSC_ARCH=arch-debug
--with-debugging=1 --download-mumps --download-scalapack<br>
[0]PETSC ERROR: #1 MatProductSymbolic() at
/home/hhornik/Software/PETSc/src/mat/interface/matproduct.c:807<br>
[0]PETSC ERROR: #2 MatProduct_Private() at
/home/hhornik/Software/PETSc/src/mat/interface/matrix.c:10027<br>
[0]PETSC ERROR: #3 MatMatMult() at
/home/hhornik/Software/PETSc/src/mat/interface/matrix.c:10103<br>
[0]PETSC ERROR: #4 PCSetUp_LSC() at
/home/hhornik/Software/PETSc/src/ksp/pc/impls/lsc/lsc.c:79<br>
[0]PETSC ERROR: #5 PCSetUp() at
/home/hhornik/Software/PETSc/src/ksp/pc/interface/precon.c:1080<br>
[0]PETSC ERROR: #6 KSPSetUp() at
/home/hhornik/Software/PETSc/src/ksp/ksp/interface/itfunc.c:415<br>
[0]PETSC ERROR: #7 KSPSolve_Private() at
/home/hhornik/Software/PETSc/src/ksp/ksp/interface/itfunc.c:832<br>
[0]PETSC ERROR: #8 KSPSolve() at
/home/hhornik/Software/PETSc/src/ksp/ksp/interface/itfunc.c:1079<br>
[0]PETSC ERROR: #9 PCApply_FieldSplit_Schur() at
/home/hhornik/Software/PETSc/src/ksp/pc/impls/fieldsplit/fieldsplit.c:1165<br>
[0]PETSC ERROR: #10 PCApply() at
/home/hhornik/Software/PETSc/src/ksp/pc/interface/precon.c:498<br>
[0]PETSC ERROR: #11 KSP_PCApply() at
/home/hhornik/Software/PETSc/include/petsc/private/kspimpl.h:383<br>
[0]PETSC ERROR: #12 KSPFGMRESCycle() at
/home/hhornik/Software/PETSc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c:123<br>
[0]PETSC ERROR: #13 KSPSolve_FGMRES() at
/home/hhornik/Software/PETSc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c:235<br>
[0]PETSC ERROR: #14 KSPSolve_Private() at
/home/hhornik/Software/PETSc/src/ksp/ksp/interface/itfunc.c:906<br>
[0]PETSC ERROR: #15 KSPSolve() at
/home/hhornik/Software/PETSc/src/ksp/ksp/interface/itfunc.c:1079<br>
[0]PETSC ERROR: #16 applySolver() at
/home/hhornik/gismo/optional/gsIncompressibleFlow/src/gsINSSolver.hpp:531</i></p>
<p><i><br>
</i>I could not find any solution for this so far. My question is:
Is it possible to use the LSC preconditioner in such case, where
the matrix blocks are of type MATNEST? And if so, how?</p>
<p>Thank you,<br>
Hana Honnerova<br>
</p>
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