Natacha BEREUX <[email protected]> writes: > OK, thanks a lot Jed for your quick answer. > > I have a second question on multigrid : > I define a matrix block size (equal to 3). Is this mandatory for any type > of multigrid preconditioner (BoomerAMG, ML and GAMG) ? > Or is it only required with ML and GAMG ?
It is always preferable. BoomerAMG distinguishes those components in its coarsening, it just doesn't use the near null space explicitly.
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