MatZeroRows and MatAssembly

[Barry Smith]

On May 28, 2008, at 9:48 AM, Gong Ding wrote:

> Hi,
> I meet some trouble about my code.
> I'd like to use MatZeroRows to perform  Dirichlet boundary condition.
> However, it requires MatAssembly, which packs the sparse matrix.
> Then the none zero pattern seems to be freezed.

    Not froozen, but yes adding more nonzeros later will be inefficient.

> The continued MatSetValues
> may be very low efficient if the item not in the previous none zero  
> pattern..

    Yes
>
>
> Is there any way to use MatZeroRows without freeze the none zero  
> pattern?

   No.

>
> Or I have to redesign my code....

    Generally you can apply the Dirichlet boundary conditions after  
you have
completely constructed the matrix.

    Barry

>
>
> Regards
> Gong Ding
>
>