"Smith, Barry F." <bsm...@mcs.anl.gov> writes: >> > The current IJacobian is essentially SNESJacobian. And the single-matrix >> > SNESJacobian interface is always there. Power users could set up the >> > SNESJacobian directly if we pass a read-only shift parameter to them. So >> > we are by no means prohibiting power users from doing what they want. >> >> You mean the user would call TSGetSNES and SNESSetJacobian, then >> internally call TSGetIJacobianShift and some new function to create >> Udot? That sounds way messier and error-prone. >> >> And completely impossible to compose. We should be explicitly talking about >> subsystems that use TS. For example, >> I have a nonlinear system for plasticity. I want to use a preconditioner >> that introduces some elasticity and timesteps to >> steady state to provide a good Newton direction. I need to to be able to >> create the solver without all sorts of digging >> in and setting things. This idea that you "just set SNESJacobian" is a >> non-starter. > > But this is exactly what TSComputeIJacobian currently does, so is the > current interface a non-starter?
It isn't at all the current interface. If the user is calling SNESSetJacobian, then we would need to open up the bowels of every SNESTSFormJacobian_* and make stable public APIs out of those internals (including the wiring for nonlinear multigrid). This sounds like a terrible thing to make public.
