[petsc-dev] Separately configuring pre and post smooth KSPs in PCMG

[Smith, Barry F.]

https://bitbucket.org/petsc/petsc/pull-requests/858/add-support-for-selecting-different-down/diff



> On Feb 14, 2018, at 5:50 AM, Lawrence Mitchell <lawrence.mitchell at imperial.ac.uk> wrote:
> 
> Dear petsc-dev,
> 
> I'd like to try out doing SOR-like smoothing for a problem with MG
> where on the pre-smooth I run forwards, and on the post-smooth backwards.
> 
> I can do this by setting up the PC and then spinning over the up and
> down smoothers separately.  I wonder if it would be possible to extend
> the setup to allow it to be done from options.
> 
> I had a look, but I got very lost in where/how the setup of the up
> smoother separate from the down smoother works.  It seems to be
> triggered on whether you select a different number of smoothing steps
> up and down, but I don't necessarily want that.
> 
> I think I just want to select a different options prefix in
> PCMGGetSmootherUp, but I can't obviously see how to ensure that's
> called appropriately.
> 
> Cheers,
> 
> Lawrence