Hi PETSc users! I have a problem that I am integrating with TS, and I think an implicit method would let me take larger timesteps. The Jacobian is difficult to compute, but, more importantly, the nonzero structure is changing with time, so even if I use coloring and finite differences to compute the actual values, I will have to update the coloring every time the Jacobian recomputes.
Has anyone done this before, and/or is there a correct way to tell TS to re-compute the coloring of the matrix before SNES actually computes the entries? Is this even a good idea, or is the coloring so expensive that this is foolish (in general -- I know the answer depends on the problem, but there may be a rule of thumb)? Thanks, Ellen Price
