It looks like it pivots in blocks and is a point-wise ILU: https://urldefense.us/v3/__https://petsc.org/release/manualpages/PC/PCILU/__;!!G_uCfscf7eWS!d82xhlyQ6-cWmSO0PBI3pnGPDROVlCOPZn87hYtI4Pi9Kkbf4wgpQjnYsrJVy0pwHGtZYvPKXDxQCoq9BTvE6Ao$
Mark On Wed, Jun 4, 2025 at 9:36 AM Frank Bramkamp <bramk...@nsc.liu.se> wrote: > Dear PETSc team, > > I have a general question regarding the implementation of the inverse > For the ILU factorization. > > I am looking e.g. on the implementation for block size 6 for the BAIJ > matrix format in serial: > src/mat/impls/baij/seq/dgefa6.c > > I wonder: > You are using pivoting in the inverse computation. > > But if one changes the position of elements or rows, do we not have to > apply an inverse permutation at the end > to get the inverse of the original matrix to some column ?! Otherwise it > is the inverse of the permutated matrix ?! > > I am not quite sure if one has to do this in principle or if my > understanding is not quite correct. > Maybe I miss something in your code. > > > Thanks, Frank > > > >
