[petsc-users] Question about TSComputeRHSJacobianConstant

[Smith, Barry F.]

> On May 22, 2019, at 2:26 PM, Sajid Ali via petsc-users <petsc-users at mcs.anl.gov> wrote:
> 
> Hi Hong, 
> 
> Looks like this is my fault since I'm using -ksp_type preonly -pc_type gamg. If I use the default ksp (GMRES) then everything works fine on a smaller problem.
> 
> Just to confirm,  -ksp_type preonly is to be used only with direct-solve preconditioners like LU,Cholesky, right ?

   You can use it any time you like but it only applies the preconditioner; thus unless your preconditioner is a really good approximation to the operator it won't give you much information.


> 
> Thank You, 
> Sajid Ali
> Applied Physics
> Northwestern University