On Wed, Jan 24, 2018 at 6:13 AM, saturday luis <[email protected]> wrote:
> Hi PETSc team: > > I am trying to solve a Stokes problem in a segregated manner, in which the > pressure field is obtained by solving the pressure Schur complement. This > is what I did. > > I created a Schur complement by calling > > Mat S; > MatCreateSchurComplement(gloAssem_ptr->K_11, gloAssem_ptr->K_11, > gloAssem_ptr->K_10, gloAssem_ptr->K_01, gloAssem_ptr->K_00, &S); > > Then I use the Mat S as an input for KSP: > KSPSetOperators(ksp, S, S); > > I got error message as follows. > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/ > linearsolvertable.html for possible LU and Cholesky solvers > [0]PETSC ERROR: Could not locate a solver package. Perhaps you must > ./configure with --download-<package> > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html > for trouble shooting. > [0]PETSC ERROR: Petsc Release Version 3.8.3, Dec, 09, 2017 > [0]PETSC ERROR: ./bipn3d on a arch-linux2-cxx-debug named bacon by luis > Tue Jan 23 11:02:34 2018 > [0]PETSC ERROR: Configure options --prefix=~/lib/petsc-3.8.3-debug > --with-x=0 -with-pic --with-mpi-compilers=1 > --with-mpi-dir=/home/lib/mpich-3.2/ > --with-clanguage=C++ --with-scalar-type=real --with-shared-libraries=1 > --with-precision=double --with-hypre=1 --download-hypre --with-spai=1 > --download-spai --with-superlu_dist=1 --download-superlu_dist > --with-superlu=1 --download-superlu --with-parmetis=1 --download-parmetis > --with-metis=1 --download-metis --with-mumps=1 --download-mumps > --with-parmetis=1 --download-parmetis --with-metis=1 --download-metis > --with-scalapack=1 --download-scalapack --with-blacs=1 --download-blacs > --with-spooles=1 --download-spooles --with-debugging=yes > --download-fblaslapack > [0]PETSC ERROR: #1 MatGetFactor() line 4346 in > /home/lib/petsc-3.8.3/src/mat/interface/matrix.c > [0]PETSC ERROR: #2 PCSetUp_ILU() line 142 in /home/lib/petsc-3.8.3/src/ksp/ > pc/impls/factor/ilu/ilu.c > [0]PETSC ERROR: #3 PCSetUp() line 924 in /home/lib/petsc-3.8.3/src/ksp/ > pc/interface/precon.c > [0]PETSC ERROR: #4 KSPSetUp() line 381 in /home/lib/petsc-3.8.3/src/ksp/ > ksp/interface/itfunc.c > [0]PETSC ERROR: #5 KSPSolve() line 612 in /home/lib/petsc-3.8.3/src/ksp/ > ksp/interface/itfunc.c > > Let me know if you can see any issue in the usage of Schur complement > creation. > This will work if you give -pc_type none which will give you plain GMRES. As Barry says, a more sophisticated thing to do is to use PCFIELDSPLIT. I do this in the examples for SNES ex62. Thanks, Matt > Thanks, > > Luis > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
