On 09/26/2017 09:42 AM, Michał Wichrowski wrote:
3) Is there a way to use multigrid on one block? For example I would
like to compute approximation of A^-1 using multigrid.
This might be the way to go since applying multigrid on the whole
saddle-point problem is difficult (but feasible).
step-22 shows how to create a preconditioner that involves A^{-1} --
take a particular look at the "Possibilities for extensions" section. I
think one of the Stokes or Navier-Stokes equation problems (54? 55? 56?
57?) may even implement something that applies multigrid already to the
A block of the Stokes system. You may then want to replace that
multigrid method by a matrix-free version. I'll let others comment on
how this can best be done.
Yours is a case that I think a lot of people would be interested in,
myself included. If you get it to work, could I interest you in thinking
about whether your program could be made into either a tutorial program
or a contribution to the code gallery?
Best
W.
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Wolfgang Bangerth email: [email protected]
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