[petsc-users] Reusing Jacobian across time steps

[Alfredo J Duarte Gomez]

Good morning PETSC team,

I am currently using a TS object to advance a set of PDEs in time.

However, the computation of the Jacobian is quite expensive and I wish to
reuse it across time steps if possible.

I am well aware of the options -snes_lag_jacobian and
-snes_lag_jacobian_persists, but I do not quite understand how to combine
them for what I want.

In summary I want to compute the Jacobian only at the beginning of a given
time step, reuse that Jacobian for N time steps, and then recompute again
at the beginning of the next time step.

With my current understanding I have been able to reuse it across time
steps by recomputing every N snes iterations, however, this leads to
recomputations in the middle of time steps which is not what I desire.

Thank you,

-Alfredo



-- 
Alfredo Duarte
Graduate Research Assistant
The University of Texas at Austin
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