[petsc-users] Scale the diagonal entries of a Mat

[Jed Brown]

Use MatSetValues with ADD_VALUES.

The method is used for toy examples because it is the most brain-dead
simple thing to implement, not because it is a good method. Much better to
lift and remove or to eliminate in-place. Any good book discusses this and
there are useful answers on scicomp.stackexchange.com.
On Feb 23, 2013 6:36 AM, "Hui Zhang" <mike.hui.zhang at hotmail.com> wrote:

>
> On Feb 23, 2013, at 1:32 PM, Jed Brown wrote:
>
> > Add big values to diagonal entries and scale the right hand side
> appropriately, as per the definition. It is a terrible method.
>
> Why?  That is what I was taught by textbooks and used by some FEM library
> like FreeFem++.
>
> >
> > On Feb 23, 2013 6:29 AM, "Hui Zhang" <mike.hui.zhang at hotmail.com> wrote:
> > I want to implement diagonal penalty method for enforcing the Dirichlet
> boundary conditions.  That is, the diagonal entries corresponding to
> Dirichlet boundary are going to be scaled by a large number.
> >
> > What is the easiest way to do this?  Thanks!
>
>
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