[petsc-users] Matrix free SNES and Jacobian, function evaluations

[Jed Brown]

The function is always evaluated before the jacobian, but sometimes the
function is evaluated at several places before a jacobian is needed (e.g. in
a line search). You can cache any information you want in the user context
during function evaluation and use it to speed up jacobian evaluation.

On Feb 9, 2011 9:22 PM, "Pearl Flath" <pflath at ices.utexas.edu> wrote:

Dear All,
I'd like to use the SNES nonlinear solvers. For my problem, evaluation of
the Jacobian and the right hand side function involves some identical steps.
I'd prefer not to repeat those, and instead have the Jacobian and function
calculation share some computations. Is there a way to do this? Does SNES
consistently evaluate one of them first, and thus I could have the other one
re-use that information? Or is there a way to tell SNES to call a general
update at each step before evaluating the Jacobian and function?

Many thanks.
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