Thank you guys for the tips. <div><br></div><div><br></div><div>Longmmin</div><div><br><div class="gmail_quote">On Tue, May 31, 2011 at 1:38 AM, Jed Brown <span dir="ltr"><<a href="mailto:jed@59a2.org">jed@59a2.org</a>></span> wrote:<br>
<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 Tue, May 31, 2011 at 01:31, Matthew Knepley <span dir="ltr"><<a href="mailto:knepley@gmail.com" target="_blank">knepley@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>You generate a NaN somewhere. I usually check for this using norms, since NaN propagate. Check the norm</div><div>of the rhs, initial solution, matrix, etc.</div></blockquote></div><br></div><div>You can also run with -fp_trap, possibly in a debugger, and it should break at the first place the NaN was computed. This works better (on more platforms) with petsc-dev.</div>
</blockquote></div><br></div>