[petsc-users] Question on PCSHELL with TS

[Jed Brown]

Praveen C <cpraveen at gmail.com> writes:

> Dear all
>
> I am trying to solve a steady state problem using TSPSEUDO and am unclear about the preconditioner. The PDE is 3-d compressible Euler/NS equations solved with FV on unstructured grids.
>
> I am using matrix-free approach (-snes_mf_operator) and want to provide my own matrix-free preconditioner using PCSHELL.
>
> For the problem
>
> du/dt = R(u)
>
> the update would be 
>
> [I - dt*J(u)]*du = dt*R(u),   J(u) = R’(u)
>
> u = u + du
>
> Does my PCSHELL have to provide a preconditioner for J or for I - dt*J ?

You'll be solving with I/dt - J.