Hello all, I would like to work out how to get nested fieldsplit to work correctly. I have a submatrix (labeled fieldsplit_P) that I would like to block precondition with sub-blocks A & B. To do this, I access the PC object within fieldsplit_P, and pass index sets corresponding to these sub-blocks (P_A_IS, P_B_IS) that tell how the matrix should be split. This is what I have:
-------------------------------------------------------------------------------- KSP *ksp_all, ksp_P; PCFieldSplitGetSubKSP(pc, &i, &ksp_all); ksp_P = ksp_all[0]; PC pc_P; KSPGetPC(ksp_P, &pc_P); // This should extract the preconditioner for fieldsplit P PCFieldSplitSetIS(pc_P, "A", P_A_IS); PCFieldSplitSetIS(pc_P, "B", P_B_IS); -------------------------------------------------------------------------------- And these are the run-time arguments: -------------------------------------------------------------------------------- -pc_type fieldsplit -pc_fieldsplit_type multiplicative -fieldsplit_P_ksp_type gmres -fieldsplit_P_pc_type fieldsplit -fieldsplit_P_pc_fieldsplit_type multiplicative -fieldsplit_P_fieldsplit_A_ksp_type gmres -fieldsplit_P_fieldsplit_B_pc_type lu -fieldsplit_P_fieldsplit_B_ksp_type preonly -------------------------------------------------------------------------------- But that does not work: -------------------------------------------------------------------------------- [0]PETSC ERROR: --------------------- Error Message -------------------------------------------------------------- [0]PETSC ERROR: No support for this operation for this object type [0]PETSC ERROR: Cannot locate function PCFieldSplitSetIS_C in object [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting. [0]PETSC ERROR: Petsc Release Version 3.7.2, Jun, 05, 2016 [0]PETSC ERROR: ./main_2D on a x86_64 named artur-ubuntu by artur Tue Jul 26 18:55:29 2016 [0]PETSC ERROR: Configure options --with-scalar-type=complex --with-mpi=1 --with-clanguage=c++ --with-cc=mpicc --with-fc=gfortran --with-cxx=mpic++ --with-fc=mpif90 --download-mumps --download-scalapack [0]PETSC ERROR: #1 PCFieldSplitSetIS() line 1756 in /home/artur/Rorsrach/Packages/petsc-3.7.2/src/ksp/pc/impls/fieldsplit/fieldsplit.c [0]PETSC ERROR: --------------------- Error Message -------------------------------------------------------------- [0]PETSC ERROR: No support for this operation for this object type [0]PETSC ERROR: Cannot locate function PCFieldSplitSetIS_C in object [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting. [0]PETSC ERROR: Petsc Release Version 3.7.2, Jun, 05, 2016 [0]PETSC ERROR: ./main_2D on a x86_64 named artur-ubuntu by artur Tue Jul 26 18:55:29 2016 [0]PETSC ERROR: Configure options --with-scalar-type=complex --with-mpi=1 --with-clanguage=c++ --with-cc=mpicc --with-fc=gfortran --with-cxx=mpic++ --with-fc=mpif90 --download-mumps --download-scalapack [0]PETSC ERROR: #2 PCFieldSplitSetIS() line 1756 in /home/artur/Rorsrach/Packages/petsc-3.7.2/src/ksp/pc/impls/fieldsplit/fieldsplit.c -------------------------------------------------------------------------------- It seems that the preconditioner object for fieldsplit_P does not know that it is also of fieldsplit type. Does anyone have any idea of how I can specify the proper fieldsplit? Best, Artur
