For a big matrix the asii output is slow (especially parallel) Yes, this view will be called automatically on all matrix when they are assembled so if you are assembling a bunch of matrices it will output them all.
You can attach a unique prefix to the matrix PetscObjectSetPrefix() and then use -uniqueprefix_mat.... You can use the binary format (faster) with -mat_view binary:ColFDJac.mat and use PetscBinaryRead() in Matlab share/petsc/matlab You can use MatView() directly in your code with a binary PetscViewer on exactly the matrix you wish to save. > On Feb 2, 2022, at 6:07 PM, Jorti, Zakariae via petsc-users > <[email protected]> wrote: > > Hello, > > I am using a TS to solve a differential algebraic equation (DAE). > I do not provide the Jacobian matrix but instead set the TS to use a finite > difference jacobian with coloring. > For debugging, I only solve this DAE on one time step. > Is there a way to output this finite difference jacobian in a matlab format > (.m file)? > I have already tried this flag : -mat_view ascii:ColFDJac.m:ascii_matlab , > but when I use it the test takes too long. My guess is that this flag is > trying to save all the matrices involved in the computations. I am only > interested in the jacobian though. > Thank you. > > Best, > > Zakariae
