<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Thanks for the suggestions guys. Barry’s field split approach gives sensible behavior. Now I’m working on tuning it.<br class=""><div class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">-gideon</span>
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<br class=""><div><blockquote type="cite" class=""><div class="">On Sep 21, 2015, at 9:21 AM, Jed Brown <<a href="mailto:jed@jedbrown.org" class="">jed@jedbrown.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">Matthew Knepley <<a href="mailto:knepley@gmail.com" class="">knepley@gmail.com</a>> writes:<br class=""><blockquote type="cite" class=""><blockquote type="cite" class="">At the same time, the first block, as discussed, has<br class="">these zeros on the diagonal, and can’t use SOR.<br class=""><br class=""></blockquote><br class="">Chebyshev/Jacobi is the obvious next try.<br class=""></blockquote><br class="">Not really; the Chebyshev polynomial exceeds 1 left of the origin, so<br class="">it's pretty non-functional on indefinite operators. Pretending like<br class="">Gideon's saddle point problem is positive definite is not a solution.<br class=""></div></blockquote></div><br class=""></body></html>