Barry Smith <[email protected]> writes: > Jed, > > Here is the problem. > > https://bitbucket.org/petsc/petsc/branch/barry/fix/even-huger-flaw-in-ts
Hmm, when someone uses -snes_mf_operator, we really just need SNESTSFormJacobian to ignore the Amat. However, the user is allowed to create a MatMFFD and have their TSRHSJacobian function use MatMFFD on their RHSFunction. That might even be more accurate, but would require the shift/scale. But I'm not aware of any way in which TS can distinguish these cases. What if SNESComputeJacobian was aware of -snes_mf_operator and just passed Pmat in both slots? Or does the user sometimes need access to the MatMFFD created by -snes_mf_operator? (Seems like possibly, e.g., to adjust differencing parameters.)
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