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.

Thank you,

-Alfredo 

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