[petsc-users] Making the convergence faster

[Jed Brown]

This is typical for weak preconditioners.  Have you tried -pc_type gamg
or -pc_type mg (algebraic and geometric multigrid, respectively)?  On a
structured grid with smooth coefficients, geometric multigrid is
possible with low setup cost and convergence in a few iterations
independent of problem size.

Maahi Talukder via petsc-users <petsc-users at mcs.anl.gov> writes:

> Dear All,
>
>
> I am solving Poisson grid generation equation  using 9-point Finite
> Difference. The type of convergence plot I am getting has been attached
> herewith. As  the plot shows, at the beginning, the convergence is very
> fast, but later the convergence is slowing down. I am using GMRES with left
> preconditioning?
>
> My question is, is it normal? Any ideas how  to make the convergence faster?
>
>
>
> Thanks,
> Maahi Talukder