> On 10 Oct 2016, at 18:19, Colin Cotter <colin.cotter@imperial.ac.uk> wrote:
>
> OK, this is the problem then - you need to find an appropriate preconditioner.
>
> You need to start by finding an appropriate preconditioner for the system without the R space part.
>
> Lawrence: once that is done, is there anything special to do to incorporate it into the system with the R space part [asking because you seem to have thought about this previously], or do we just recommend block preconditioning in this case?

I think you could use block first.  It's easier.  Otherwise I think the firedrake webpages sketch how to do sherman-morrison.

Lawrence
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