Block matrices can use block smoothers, which invert whole blocks exactly. This can<br>be much more effective than point smoothers if you actually have block structure in<br>the matrix.<br><br> Matt<br><br><div class="gmail_quote">
On Thu, May 21, 2009 at 10:45 PM, Ryan Yan <span dir="ltr"><<a href="mailto:vyan2000@gmail.com">vyan2000@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi all,<br>I did a numerical experiment of ksp solve on a large sparse matrix.<br><br>For the first step, I load the matrix from petsc readable files. If I load the matrix as a MPIAIJ matrix and then apply the prometheus preconditioner with GMRES, it will not converge in 10000 iterations.<br>
<br>However, if I load the matrix as a MPIBAIJ matrix and then apply the prometheus preconditioner with GEMRES, it will converge with in 800 iterations<br><br>Can anyone please provide some hints on how to explain this numerical result.<br>
<br>Thanks a lot, <br><font color="#888888"><br>Yan<br>
</font></blockquote></div><br><br clear="all"><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>