<div class="gmail_quote">On Wed, May 11, 2011 at 04:20, Sylvain Barbot <span dir="ltr"><<a href="mailto:sylbar.vainbot@gmail.com">sylbar.vainbot@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":2ag">I am still trying to design a<br>
multigrid preconditionner for the Navier's equation of elasticity.</div></blockquote></div><br><div>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.</div>
<div><br></div><div>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.</div>