Michele Rosso <[email protected]> writes: > Jed, > > thank you very much! > I will try with ///-mg_levels_ksp_type chebyshev -mg_levels_pc_type > sor/ and report back. > Yes, I removed the nullspace from both the system matrix and the rhs. > Is there a way to have something similar to Dendy's multigrid or the > deflated conjugate gradient method with PETSc?
Dendy's MG needs geometry. The algorithm to produce the interpolation operators is not terribly complicated so it could be done, though DMDA support for cell-centered is a somewhat awkward. "Deflated CG" can mean lots of things so you'll have to be more precise. (Most everything in the "deflation" world has a clear analogue in the MG world, but the deflation community doesn't have a precise language to talk about their methods so you always have to read the paper carefully to find out if it's completely standard or if there is something new.)
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