<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" id="owaParaStyle"></style>
</head>
<body class="" style="word-wrap:break-word" fpstyle="1" ocsi="0">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">
<div><br>
</div>
Hi Marco,
<div><br>
</div>
<div>Here is the reference:</div>
<div><br>
</div>
<div>
<ol style="font-family: -webkit-standard;">
<li>Fischer, P.F., <a href="http://www.mcs.anl.gov/~fischer/pubhtml/project.pdf">"Projection techniques for iterative solution of Ax=b with successive right-hand sides." </a><em>Comp. Meth. in Appl. Mech</em> <b>163</b> (1998).
<p></p>
</li></ol>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"> </div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">There is also a 1993 ICASE Report, but it's mostly a subset of this paper. </div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"><br>
</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">Paul</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"><br>
</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">PS - these typical values are based on my experience... but, it's easy to try a run for a few</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">hundred steps and see which parameters make things run faster.</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"><br>
</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"><br>
</div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px"><br>
<hr tabindex="-1">
<div id="divRpF144914" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> nek5000-users-bounces@lists.mcs.anl.gov [nek5000-users-bounces@lists.mcs.anl.gov] on behalf of nek5000-users@lists.mcs.anl.gov [nek5000-users@lists.mcs.anl.gov]<br>
<b>Sent:</b> Monday, June 27, 2016 8:01 AM<br>
<b>To:</b> nek5000-users@lists.mcs.anl.gov<br>
<b>Subject:</b> Re: [Nek5000-users] Projection technique's parameters<br>
</font><br>
</div>
<div></div>
<div>Paul,
<div class=""><br class="">
</div>
<div class="">is there a paper/report we can have access to that goes in the details of the implementation, please? Also, are the typical values based on your personal experience?</div>
<div class=""><br class="">
</div>
<div class="">Thanks,</div>
<div class="">Marco<br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Jun 27, 2016, at 8:55 AM, <a href="mailto:nek5000-users@lists.mcs.anl.gov" class="" target="_blank">
nek5000-users@lists.mcs.anl.gov</a> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="" style="font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px; direction:ltr; font-family:Tahoma; font-size:10pt">
<br class="Apple-interchange-newline">
Hi Andrew,
<div class=""><br class="">
</div>
<div class="">The projection routines are currently being overhauled, but the general strategy is:</div>
<div class=""><br class="">
</div>
<div class=""> Number of projections controlled by p93 and mxprev in SIZE. </div>
<div class=""><br class="">
</div>
<div class=""> p94 > 0: start projecting velocity/temp after step p94</div>
<div class=""><br class="">
</div>
<div class=""> p95 > 0: start projecting pressure after step 95</div>
<div class=""><br class="">
</div>
<div class="">I typically set p94 and p95 to 5</div>
<div class=""><br class="">
</div>
<div class="">I set mxprev and p93 to 20, but sometimes to a higher value.</div>
<div class=""><br class="">
</div>
<div class="">I used to occasionally to to much higher than 20 (say, 80), but in a recent</div>
<div class="">rewrite and effort to make projection more robust I slowed the projection</div>
<div class="">step down with too much work, so another rewrite is due soon.</div>
<div class=""><br class="">
</div>
<div class="">Paul</div>
<div class=""><br class="">
</div>
<div class="">PS - note that certain combinations of run parameters don't support</div>
<div class="">projection or potentially blow up. Set p94=0 in this case and retry.</div>
<div class="">There was a bug that was fixed about 6 weeks back---it may have cured</div>
<div class="">some of the cases that users were running into.</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
<div class="" style="font-family:'Times New Roman'; font-size:16px">
<hr tabindex="-1" class="">
<div id="divRpF765626" class="" style="direction:ltr"><font face="Tahoma" size="2" class=""><b class="">From:</b><span class="Apple-converted-space"> </span><a href="mailto:nek5000-users-bounces@lists.mcs.anl.gov" class="" target="_blank">nek5000-users-bounces@lists.mcs.anl.gov</a>
[<a href="mailto:nek5000-users-bounces@lists.mcs.anl.gov" class="" target="_blank">nek5000-users-bounces@lists.mcs.anl.gov</a>] on behalf of
<a href="mailto:nek5000-users@lists.mcs.anl.gov" class="" target="_blank">nek5000-users@lists.mcs.anl.gov</a> [<a href="mailto:nek5000-users@lists.mcs.anl.gov" class="" target="_blank">nek5000-users@lists.mcs.anl.gov</a>]<br class="">
<b class="">Sent:</b><span class="Apple-converted-space"> </span>Monday, June 27, 2016 3:17 AM<br class="">
<b class="">To:</b><span class="Apple-converted-space"> </span><a href="mailto:nek5000-users@lists.mcs.anl.gov" class="" target="_blank">nek5000-users@lists.mcs.anl.gov</a><br class="">
<b class="">Subject:</b><span class="Apple-converted-space"> </span>[Nek5000-users] Projection technique's parameters<br class="">
</font><br class="">
</div>
<div class=""></div>
<div class="">
<div dir="ltr" class=""><span lang="en" class=""><span class="">Hi Neks,<br class="">
<br class="">
</span></span>My question is about the parameters which manage the projection method in the NEK5000: p93, p94 and p95. How can the correct values be selected for these parameters to obtain the better performance depending on the nature of simulation: laminar
/ turbulent, convection / diffusion, time step?<br class="">
<br class="">
<span lang="en" class="">Thank you for any suggestion,<span class="Apple-converted-space"> </span><br class="">
</span><span lang="en" class="">Andrew</span><br class="">
</div>
</div>
</div>
</div>
</div>
<span class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px; float:none; display:inline!important">_______________________________________________</span><br class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px">
<span class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px; float:none; display:inline!important">Nek5000-users
mailing list</span><br class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px">
<span class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px; float:none; display:inline!important"><a href="mailto:Nek5000-users@lists.mcs.anl.gov" class="" target="_blank">Nek5000-users@lists.mcs.anl.gov</a></span><br class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px">
<span class="" style="font-family:Helvetica; font-size:12px; font-style:normal; font-weight:normal; letter-spacing:normal; orphans:auto; text-align:start; text-indent:0px; text-transform:none; white-space:normal; widows:auto; word-spacing:0px; float:none; display:inline!important"><a href="https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users" class="" target="_blank">https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users</a></span></div>
</blockquote>
</div>
<br class="">
</div>
</div>
</div>
</div>
</div>
</body>
</html>