Dear all, I am coupling my unstructured CFD solver with PETSc. At this moment, sequential version is working fine, but I obviously want to migrate to MPI parallel. My code is MPI parallel since ages. Anyhow, as a part of the migration to parallel, I changed the matrix type from MATSEQAIJ to MATMPIAIJ. The code compiled, but when I executed it one processor, I received an error message that combination of matrix format does not support BICG solver and PCILU preconditoner. I took a look at the compatibility matrix ( https://petsc.org/release/overview/linear_solve_table/#preconditioners) and noticed that MATMPIAIJ supports only MKL CParadiso preconditioner which seems to belong to Intel. I did some more reading and realised that I should probably continue with MATAIJ (which should work in sequential and parallel), but I am wondering why would there even be MATMPIAJ if it supports only one third-party preconditioner? Cheers, Bojan Niceno