Are you using serial SuperLU, or distributed-memory SuperLU_DIST? What are the algorithm options are you using?
Sherry Li On Thu, Jun 9, 2022 at 2:20 PM Jorti, Zakariae via petsc-users < [email protected]> wrote: > Hi, > > I am solving non-linear problem that has 5 unknowns {ni, T, E, B, V}, and > for the preconditioning part, I am using a FieldSplit preconditioner. At > the last fieldsplit/level, we are left with a {B,V} block that tried to > precondition in 2 different ways: > a) SuperLU: > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_ksp_type preonly > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_pc_type lu > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_pc_factor_mat_solver_type > superlu_dist > b) a Schur-based fieldsplit preconditioner that uses SuperLU for both V > and B blocks: > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_ksp_type gmres > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_pc_type fieldsplit > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_pc_fieldsplit_type schur > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_pc_fieldsplit_schur_precondition > selfp -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_B_ksp_type > preonly -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_B_pc_type > lu > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_B_pc_factor_mat_solver_type > superlu_dist > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_V_ksp_type preonly > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_V_pc_type lu > -fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_fieldsplit_V_pc_factor_mat_solver_type > superlu_dist > > Option a) yields the following error: > " Linear fieldsplit_ni_ solve converged due to CONVERGED_ATOL > iterations 0 > Linear fieldsplit_TEBV_fieldsplit_tau_ solve converged due to > CONVERGED_RTOL iterations 1 > Linear fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_EP_ solve > converged due to CONVERGED_RTOL iterations 5 > Linear fieldsplit_TEBV_fieldsplit_EBV_fieldsplit_BV_ solve did > not converge due to DIVERGED_PC_FAILED iterations 0 > PC failed due to FACTOR_NUMERIC_ZEROPIVOT " > whereas options b) seems to be working well. > Is it possible that the SuperLU on the {V,B} block uses a reordering that > introduces a zero pivot or could there be another explanation for this > error? > > Many thanks. > Best, > > Zakariae > >
