<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">OK I see what you mean now.  </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">Thanks a lot for the help, playing with the inner tolerances was the key to </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">improve the performance of the PCFieldSplit preconditioner.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">The only question which still remains is when should one use preonly for the inner solves.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div>You could try to play games with the inner tolerances (say run the blocks only to 10^-4). However,</div><div>the fact remains that this is not even a credible solver for the problem.</div><span class=""><div><br></div><div>  Thanks,</div><div><br></div><div>     Matt</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><div style="font-family:arial,helvetica,sans-serif;font-size:small">Best regards,</div><div style="font-family:arial,helvetica,sans-serif;font-size:small">Bernardo​</div><br></div></div></div></div>
</blockquote></span></div><span class=""><br><br clear="all"><div><br></div>-- <br><div class="m_-2872516975850382540gmail_signature"><div dir="ltr"><div><div dir="ltr"><div>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</div><div><br></div><div><a href="http://www.caam.rice.edu/~mk51/" target="_blank">https://www.cse.buffalo.edu/~<wbr>knepley/</a><br></div></div></div></div></div>
</span></div></div>
</blockquote></div><br></div></div>