On Mon, Dec 13, 2021 at 1:16 PM Dave May <[email protected]> wrote:
> > > On Sat 11. Dec 2021 at 22:28, Matthew Knepley <[email protected]> wrote: > >> On Sat, Dec 11, 2021 at 1:58 PM Tang, Qi <[email protected]> wrote: >> >>> Hi, >>> Does anyone have comment on finite difference coloring with DMStag? We >>> are using DMStag and TS to evolve some nonlinear equations implicitly. It >>> would be helpful to have the coloring Jacobian option with that. >>> >> >> Since DMStag produces the Jacobian connectivity, >> > > This is incorrect. > The DMCreateMatrix implementation for DMSTAG only sets the number of > nonzeros (very inaccurately). It does not insert any zero values and thus > the nonzero structure is actually not defined. > That is why coloring doesn’t work. > Ah, thanks Dave. Okay, we should fix that.It is perfectly possible to compute the nonzero pattern from the DMStag information. Paging Patrick :) Thanks, Matt > Thanks, > Dave > > > you can use -snes_fd_color_use_mat. It has many options. Here is an >> example of us using that: >> >> >> https://gitlab.com/petsc/petsc/-/blob/main/src/snes/tutorials/ex19.c#L898 >> >> Thanks, >> >> Matt >> >> >>> Thanks, >>> Qi >>> >>> >>> On Oct 15, 2021, at 3:07 PM, Jorti, Zakariae via petsc-users < >>> [email protected]> wrote: >>> >>> Hello, >>> >>> Does the Jacobian approximation using coloring and finite differencing >>> of the function evaluation work in DMStag? >>> Thank you. >>> Best regards, >>> >>> Zakariae >>> >>> >>> >> >> -- >> 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/> >> > -- 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/>
