Dear firedrakers, I’m trying to extract the components of the field split preconditioner to time them individually, but it fails. I suspect that I’mnot setting up some things, but it’s not obvious what to do. For example, if I do ksp = up_solver.snes.getKSP() ksp.setUp() ksp_hdiv, ksp_schur = ksp.getPC().getFieldSplitSubKSP() # HDiv space ksp_hdiv.setUp() op_hdiv, op_pc_hdiv = ksp_hdiv.getOperators() pc_hdiv = ksp_hdiv.getPC() print pc_hdiv.getType() ndof = op_hdiv.getSizes()[0][0] x = PETSc.Vec() x.create() x.setSizes((ndof, None)) x.setFromOptions() x.setArray(np.random.rand(ndof)) y = x.duplicate() x.setArray(np.zeros(ndof)) pc_hdiv.apply(x,y) with timed_region('pc_hdiv'): pc_hdiv.apply(x,y) I get: bjacobi Traceback (most recent call last): File "driver.py", line 557, in <module> main(parameter_filename) File "driver.py", line 499, in main pc_hdiv.apply(x,y) File "PC.pyx", line 187, in petsc4py.PETSc.PC.apply (src/petsc4py.PETSc.c:132142) petsc4py.PETSc.Error: error code 71 [0] PCApply() line 449 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/pc/interface/precon.c [0] PCApply_BJacobi_Singleblock() line 670 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/pc/impls/bjacobi/bjacobi.c [0] KSPSolve() line 542 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/ksp/interface/itfunc.c [0] KSPSetUp() line 330 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/ksp/interface/itfunc.c [0] PCSetUp() line 918 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/pc/interface/precon.c [0] PCSetUp_ILU() line 232 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/ksp/pc/impls/factor/ilu/ilu.c [0] MatLUFactorNumeric() line 2945 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/mat/interface/matrix.c [0] MatLUFactorNumeric_SeqAIJ() line 566 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/src/mat/impls/aij/seq/aijfact.c [0] MatPivotCheck() line 664 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/include/petsc-private/matimpl.h [0] MatPivotCheck_none() line 645 in /Users/eikemueller/PostDocBath/EllipticSolvers/petsc/include/petsc-private/matimpl.h [0] Zero pivot in LU factorization: http://www.mcs.anl.gov/petsc/documentation/faq.html#ZeroPivot [0] Zero pivot row 0 value 0 tolerance 2.22045e-14 so it looks to me like the PC is not set up correctly. I use 'fieldsplit_0_ksp_type': 'preonly', 'fieldsplit_0_pc_type': 'bjacobi', 'fieldsplit_0_sub_pc_type': 'ilu’, So I suspect the ILU has not been set up correctly Thanks, Eike The solver parameters are: sparams={'pc_type': 'fieldsplit', 'pc_fieldsplit_type': 'schur', 'ksp_type': 'gmres', 'ksp_max_it': 100, 'ksp_rtol':self._tolerance, 'pc_fieldsplit_schur_fact_type': 'FULL', 'pc_fieldsplit_schur_precondition': 'selfp', 'fieldsplit_0_ksp_type': 'preonly', 'fieldsplit_0_pc_type': 'bjacobi', 'fieldsplit_0_sub_pc_type': 'ilu', 'fieldsplit_1_ksp_type': 'preonly', 'fieldsplit_1_pc_type': 'gamg', 'fieldsplit_1_mg_levels_ksp_type': 'chebyshev', 'fieldsplit_1_mg_levels_ksp_chebyshev_estimate_eigenvalues': True, 'fieldsplit_1_mg_levels_ksp_chebyshev_estimate_eigenvalues_random': True, 'fieldsplit_1_mg_levels_ksp_max_it': 1, 'fieldsplit_1_mg_levels_pc_type': 'bjacobi', 'fieldsplit_1_mg_levels_sub_pc_type': 'ilu', 'ksp_monitor': False}