PCLU#

Uses a direct solver, based on LU factorization, as a preconditioner

Options Database Keys#

-pc_factor_reuse_ordering - Activate PCFactorSetReuseOrdering()
-pc_factor_mat_solver_type - Actives PCFactorSetMatSolverType() to choose the direct solver, like superlu
-pc_factor_reuse_fill - Activates PCFactorSetReuseFill()
-pc_factor_fill - Sets fill amount
-pc_factor_in_place - Activates in-place factorization
-pc_factor_mat_ordering_type <nd,rcm,…> - Sets ordering routine
-pc_factor_pivot_in_blocks <true,false> - allow pivoting within the small blocks during factorization (may increase stability of factorization.
-pc_factor_shift_type - Sets shift type or -1 for the default; use ‘-help’ for a list of available types
-pc_factor_shift_amount - Sets shift amount or -1 for the default
-pc_factor_nonzeros_along_diagonal - permutes the rows and columns to try to put nonzero value along the diagonal.
-pc_factor_mat_solver_type - use an external package for the solve, see MatSolverType for possibilities
-mat_solvertype_optionname - options for a specific solver package, for example -mat_mumps_cntl_1

Notes#

Not all options work for all matrix formats

Run with -help to see additional options for particular matrix formats or factorization algorithms

Usually this will compute an “exact” solution in one iteration and does not need a Krylov method (i.e. you can use -ksp_type preonly, or KSPSetType(ksp,KSPPREONLY) for the Krylov method