[petsc-dev] TS alpha parameter for preconditioner function

[Ben Dudson]

Hello

I'm using the petsc-dev TS system to solve a system

u' = F(u)

and would like to supply my own preconditioner to the KSP linear solver 
inside the SNES nonlinear solver. The Jacobian of the system is difficult 
to evaluate, so I would like to remain matrix-free. I have however got an 
approximate inverse operator of the linear system being solved by KSP:

(I - alpha*J)

In SUNDIALS it's possible to supply a preconditioner function which is then 
called passing the system state, vector to be preconditioned, and the alpha 
parameter. To do this in PETSc, should I define a MatShell or PCShell, and 
is there a way to get alpha from the TS?

Thanks in advance

Ben Dudson
Department of Physics
University of York