Comment 3 for bug 1129092

On 18 February 2013 19:05, James Maddison <email address hidden> wrote:
> I've used this for symmetric bc application. I have a very specific case
> where full system assembly is not appropriate -- for example, the RHS
> vector may have been cached without bcs, and then just the bc term needs
> to be added. I'm open to using an alternative approach if one is
> appropriate.
>

It's easy to write a cut-down assembler for special applications.

> What is the cause of a loss of parallel performance?
>

It will be bad is serial, and worse in parallel, because the matrix is
stored in compressed sparse row format. Finding column entries
requires a lot of searching. Columns are spread across processes.

Garth

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> Title:
> DirichletBC::zero_columns is very slow
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