[petsc-users] V-cycle multigrid with matrix shells

[Jed Brown]

On Wed, May 11, 2011 at 04:20, Sylvain Barbot <sylbar.vainbot at gmail.com>wrote:

> I am still trying to design a
> multigrid preconditionner for the Navier's equation of elasticity.
>

I have heard, through an external source, that you have large jumps in both
Young's modulus and Poisson ratio that are not grid aligned, including
perhaps thin structures that span a large part of the domain. Such problems
are pretty hard, so I suggest you focus on robustness and do not worry about
low-memory implementation at this point. That is, you should assemble the
matrices in a usual PETSc format instead of using MatShell to do everything
matrix-free. This gives you access to much stronger smoothers.

After you find a scheme that is robust enough for your purposes, _then_ you
can make it low-memory by replacing some assembled matrices by MatShell. To
realize most of the possible memory savings, it should be sufficient to do
this on the finest level only.
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