<div dir="ltr"><div class="gmail_quote">On Fri, Apr 8, 2011 at 11:40, <span dir="ltr"><<a href="mailto:domenico.borzacchiello@univ-st-etienne.fr">domenico.borzacchiello@univ-st-etienne.fr</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div id=":6wm">I can't get why it takes more than one Newton iteration even if my system<br>
is linear and the linear solver is direct.<br></div></blockquote><div><br></div><div>The direct solver should also converge in one iteration. Are you only assembling an approximation of the Jacobian (e.g. using -snes_mf_operator)? If using MFFD, is the system poorly scaled such that the step size is very low accuracy (maybe try -mat_mffd_type ds)? Are the equations singular? Is both the Jacobian and residual evaluation correct?</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div id=":6wm">
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As for the Vanka smoother would you suggest to implement it with PCSHELL<br>
or by defining a new PC type?</div></blockquote></div><br><div>That is up to you. Defining a new PC type makes it more reusable, but PCShell is a bit quicker to develop. You can start with PCShell and convert it later.</div>
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