[petsc-users] Examples on solving linear systems using GMRES and/or matrix-free method

[Matthew Knepley]

On Tue, Jun 7, 2011 at 10:20 PM, Xiang Hao <haoxiang at yahoo.cn> wrote:

> Hi all,
>
> I need to solve a PDE ( basically a Poisson's equation with Neumann
> boundary condition ), and I solved it using a steepest descent method, which
> is very slow. Now I want to solve the PDE using GMRES. In addition, I do
> have the matrix A, but I have a function which computes Ax, so I also need
> to use the matrix free method.
>
> I am very new to PETSc, so I am looking for examples on solving linear
> systems using GMRES and/or matrix-free method.
>

You can look at SNES ex5 for the Poisson equation (after setting lambda =
0.0). SNES ex19 also shows how to use geometric Multigrid.
Its not hard to do this for Poisson.

  Thanks,

     Matt


> Thanks,
> Xiang
>
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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