On Sep 2, 2021, at 9:24 AM, Alfredo J Duarte Gomez <[email protected]<mailto:[email protected]>> wrote: Good morning PETSC team, I am looking to implement a fully implicit BDF-DAE solver and I came across the TSBDF object https://petsc.org/release/src/ts/impls/bdf/bdf.c.html#TSBDF. This seems to be exactly what I am looking for, but I still have questions and I can't seem to find much from it in the documentation or the users manual. The key question for me is whether this is implementation is a Variable Leading Coefficient BDF or Fixed-Leading Coefficient BDF (such as CVODE). This impacts my ability of reusing matrix factorizations. It is not FLC BDF. It uses the classic variable-step formula that computes the coefficients from the last stepsizes. Hong (Mr.) Thank you, -Alfredo -- Alfredo Duarte Graduate Research Assistant The University of Texas at Austin