On Mon, Jan 9, 2012 at 10:31 AM, Alexander Grayver <span dir="ltr"><<a href="mailto:agrayver@gfz-potsdam.de">agrayver@gfz-potsdam.de</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">
I have tested default GMRES+ILU(0) solver for problem of size ~200000 and I observed that both convergence rate and accuracy degrade when I increase number of processes.<br>
E.g., number of iterations almost doubles when going from 1 to 4 processors.<br>
<br>
I noticed that ILU(0) is somehow represented by sequential matrices internally and feel that this might be a reason?<br></blockquote><div><br></div><div>The default is Block Jacobi+ILU(0) and GMRES(30) which will definitely degrade as the number of</div>
<div>processes is increased. You would need to use an optimal preconditioner like Multigrid if you want</div><div>a constant number of iterates.</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Regards,<br>
Alexander<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <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>