Hi Dave,
Thanks for the tip - you were right, and this works better for higher
resolutions now.
all the best
--Colin
From: Dave May
Sent: 19 March 2019 11:25:11
To: Cotter, Colin J
Cc: petsc-users@mcs.anl.gov
Subject: Re: [petsc-users] Confusing Schur
Hi Colin,
On Tue, 19 Mar 2019 at 09:33, Cotter, Colin J
wrote:
> Hi Dave,
>
> >If you are doing that, then you need to tell fieldsplit to use the Amat
> to define the splits otherwise it will define the Schur compliment as
> >S = B22 - B21 inv(B11) B12
> >preconditiones with B22, where as what
Hi Dave,
>If you are doing that, then you need to tell fieldsplit to use the Amat to
>define the splits otherwise it will define the Schur compliment as
>S = B22 - B21 inv(B11) B12
>preconditiones with B22, where as what you want is
>S = A22 - A21 inv(A11) A12
>preconditioned with B22.
>If your
preconditioner for the Schur system.
> --
> *From:* petsc-users on behalf of
> Cotter, Colin J via petsc-users
> *Sent:* 18 March 2019 20:14:48
> *To:* petsc-users@mcs.anl.gov
> *Subject:* [petsc-users] Confusing Schur preconditioner behaviour
>
>
Dear petsc-users,
I'm solving a 2x2 block system, for which I can construct the Schur
complement analytically (through compatible FEM stuff),
which I can pass as the preconditioning matrix.
When using gmres on the outer iteration, and preonly+lu on the inner iterations
with a Schur
