[petsc-users] GAMG and near-null-space when applying Dirichlet Conditions

[Matthew Knepley]

On Wed, Feb 24, 2016 at 9:45 AM, Manav Bhatia <bhatiamanav at gmail.com> wrote:

> Hi,
>
>     I typically apply Dirichlet BCs by modifying the Jacobin and rhs: zero
> constrained rows of matrix with 1.0 at diagonal, and zero corresponding
> rows of rhs.
>
>     While using GAMG, is it still recommended to provide the near-null
> space (given that the zero-eigenvalues have been removed by specification
> of DIrichlet BCs)?
>

Yes.


>     If that information is still needed, should the vectors be modified in
> any manner to be consistent with the Dirichlet BCs?
>

No. You can see that if you take a small piece of the domain, apart from
the boundary, it will have this as a null space.

  Matt


> Thanks,
> Manav
>
>
>


-- 
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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