[petsc-users] Jacobian free solve and preconditioning

[Shiva Rudraraju]

Hi,

My problem (finite strain mechanics with additional higher order gradient terms) involves a very complex jacobian.  To avoid mistakes from hand coding the jacobian I use AD (Sacado/Adept). However, both the hand coded jacobian evaluation and AD computation of jacobian are computationally very expensive and compete-with/exceed the solve time. So I am looking at Jacobian free approchaes….and would want to have some sort of matrix free preconditioning. I am thinking of using:

-ksp_type fgmres -pc_type ksp -ksp_ksp_type gmres -ksp_pc_type jacobi -snes_mf 

But -snes_mf will not use any preconditioner, so I want to try something like -snes_mf_operator, but which uses GMRES/BiCG as a preconditioner without the need for explicit jacobian computation. However, snes_mf_operator requires the Jacobian function….. Any way to obtain jacobian free preconditioning?

Thanks,
Shiva


Shiva Rudraraju
Asst. Research Scientist,
University of Michigan Ann Arbor.