Hello,
I could have posted my message on the user list but it seems to me that
it's more in the petsc development part. Don't hesitate to tell me if
I'm wrong.
I am developing a code called cafes that studies fluid-particle
interactions in a Stokes fluid. For that, we implemented the whole
solver in matrix free on a cartesian grid. The preconditioner is
naturally a geometrical multigrid for the velocity. The set of matrix
free for each level is set by hand (I worked with Matthew on this a long
time ago now!).
I would have liked to implement telescope on this part. I started it but
I didn't get out of it. So I would like to have your help.
What I tried to do was to describe my classical multigrid up to a level
N1 and then take the coarse solver and apply the telescope
preconditioner to it up to a level N2. I don't know if this is the best
way but it seemed the most intuitive. The problem is that I could not
get the coarse matrix because the setup is not done yet (I use a
DMKSPSetComputeOperators for the matrices).
The construction of the matrix free for each level is here:
https://github.com/gouarin/cafes/blob/master/cafes/problem/stokes.hpp#L59-L88
The description of the Stokes preconditioner is described here :
https://github.com/gouarin/cafes/blob/master/cafes/problem/stokes.hpp#L109-L162
I have tried multiple implementations without success. For me, the start
is to add at line 105 something like
KSP coarse;
ierr = PCMGGetCoarseSolve(pc_i, &coarse);CHKERRQ(ierr);
PC pc_coarse;
ierr = KSPGetPC(coarse, &pc_coarse);CHKERRQ(ierr);
ierr = PCSetType(pc_coarse, PCTELESCOPE);CHKERRQ(ierr);
Then, to create the several matrices of the levels of TELESCOPE, I
thought using the same process as before with DMKSPSetComputeOperators.
But it doesn't work...
Could you tell me how I can make it work ?
Thanks,
Loic
