On Mon, Aug 8, 2011 at 10:31 PM, Jed Brown <span dir="ltr"><<a href="mailto:jedbrown@mcs.anl.gov">jedbrown@mcs.anl.gov</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><div class="gmail_quote">On Mon, Aug 8, 2011 at 17:16, Barry Smith <span dir="ltr"><<a href="mailto:bsmith@mcs.anl.gov" target="_blank">bsmith@mcs.anl.gov</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>Add a KSP/SNES./TSSetDirichlet(ksp,snes,ts,IS listofnodes,Vec valuesfornodes)?</div></blockquote></div><br></div><div>This might be worthwhile. It needs a new Mat primitive which zeros the rows and columns while also "remembering" the column values that it zeroed (as another assembled matrix). I think it's best to apply the transformation immediately after residuals are calculated so that norms are correct (not in KSP at all). Matrix values are not available at this time so the Dirichlet equations may not be scaled correctly for GMG. We have to be careful that the residual evaluation passed to MatMFFD has the Dirichlet projection inside it.</div>
</blockquote></div><br>This is exactly the reason that I abandoned this approach when I got to nonlinear equations. It is complex and fragile, and requires that too<div>many things be coordinated out of sight of the user.<br clear="all">
<br></div><div> Matt</div><div><br>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener<br>
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