Barry Smith <[email protected]> writes: > There is the same issue with ODE integrators for linear problems. The > solvers tromp on the Jacobian.
So with TS, the shift comes from a mass matrix and that matrix could conceivably change independent of whether the (RHS) Jacobian has changed. > We should actually add an error indicator in these TAO/TS solvers, if the > "Jacobian" state value is not increased in the next time step/iteration this > means the person did not supply the new Jacobian (in other words the Jacobian > is still whatever it was tromped to) so the solver should error out and tell > the user their mistake. But with TAO, isn't the shift always diagonal? It seems wasteful to always do a full assembly (or store a pristine copy) when only a modified shift is needed. If there is a simple and reliable way to correct the shift, it would be a nicer interface to just do the right thing. Note that TS is extra confusing because the user can pass IJacobian, RHSJacobian, or both, and we reuse whichever matrix they provide.
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