Do you mean a piecewise smooth function, with a discontinuous derivative,
or a piecewise function which is itself discontinuous?
Thanks,
Matt
On Tue, May 5, 2020 at 11:05 PM Yingjie Wu <yjw...@gmail.com> wrote:
> Dear PETSc developers
> Hi,
>
> I have been using SNES to solve a nonlinear problem recently, but this
> nonlinear problem is different from the ordinary problem, in which its
> residual function is a piecewise function. I have the following questions
> during calculation:
>
>
> 1. As I am not very familiar with the jacobian matrix construction of
> this piecewise function, I used the - snes_fd. However, the result is not
> converged in process of calculation. I don't know if it's the piecewise
> function problem or other errors.
> 2. For this piecewise function problem, it is actually determination
> of the residual function according to the current solution vector. Should I
> determine the piecewise function before each Newton step begins, or add
> judgment directly to the evaluation function to form the piecewise
> function? Now I'm adding judgment directly to the evaluation function to
> form a piecewise function.
> 3. Are there some special treatment for piecewise residual functions
> in the SNES?
>
> I'm dealing with a water two-phase flow problem, which is difficult to
> describe in detail because the model is relatively complex. For the first
> time I have encountered this problem and hope to get some advice or
> information.
>
>
> Thanks,
>
> Yingjie
>
--
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/>
