<div class="gmail_quote">On Fri, Jun 17, 2011 at 12:35, Tian(ICT) <span dir="ltr"><<a href="mailto:rongtian@ncic.ac.cn">rongtian@ncic.ac.cn</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
If I test the code with and without -snes_mf_operator and the
SNES solve gives the "exactly" same solution (can they be the
exactly same?</blockquote><div><br></div><div>They won't be exactly the same because the finite differenced Jacobian has more and different rounding errors from an analytic Jacobian. But they should agree to about sqrt(epsilon) which is about 7 significant digits for double precision.</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">, can I say the analytic Jacobian is correct?</blockquote></div><br><div>Yes, provided the problem you ran it on exercises all nonlinear terms in your equations.</div>