On Tue, May 3, 2022 at 2:58 AM Pierre Seize <[email protected]> wrote:
> Hi, > > If I may, is this what you want ? > > https://petsc.org/main/docs/manualpages/SNES/SNESSetLagJacobian.html Yes, this is a good suggestion. Also, you could implement an approximation to the Jacobian. You could then improve it at each iteration using a secant update. This is what the Generalized Broyden methods do. We call them NGMRES. Thanks, Matt > Pierre > > On 03/05/2022 06:21, Tang, Qi wrote: > > Hi, > > Our code uses FDcoloring to compute Jacobian. The log file indicates > most of time is spent in evaluating residual (2600 times in one Newton > solve) while it only needs 3 nonlinear iterations and 6 total linear > iterations thanks to the fieldsplit pc. > > > > As a temporary solution, is it possible to evaluate Jacobian only once > in one Newton solve? This should work well based on my other experience if > pc is very efficient. But I cannot find such a flag. > > > > Is there any other solution, other than implementing the analytical > Jacobian? > > > > Thanks, > > Qi > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
