[petsc-users] Coloring of a parallel matrix

[Barry Smith]

On Sep 7, 2011, at 3:00 AM, Jed Brown wrote:

> On Wed, Sep 7, 2011 at 08:59, Kostas Kontzialis <ckontzialis at lycos.com> wrote:
>  I'm using a matrix free method for the solution of the Navier-Stokes equaiotns on unstructured meshes. I want to numerically evaluate the elements of the residual's Jacobian matrix. I know  where the non zero elements of the matrix are, but I read on the manual, that function MatGetColoring works only on sequential matrices. What should I do?
> 
> It actually works for parallel matrices, but the underlying algorithm is serial.  You can use it for tests and small problems, but it does not scale.

    Even though it does not scale for super large problems the algorithms are pretty fast so you can likely run parallel problems with matrices up to a few million (sparse) rows and it will likely run satisfactory.

    Barry

> 
> PETSc does not currently have a parallel graph coloring implementation, so you would have to compute a coloring yourself if you intend to use this for larger problem sizes.