<html><body><div style="color:#000; background-color:#fff; font-family:verdana, helvetica, sans-serif;font-size:10pt"><div style="font-family: verdana, helvetica, sans-serif; "><br></div><div><blockquote style="border-left-width: 2px; border-left-style: solid; border-left-color: rgb(16, 16, 255); margin-left: 5px; margin-top: 5px; padding-left: 5px; "> <div style="font-size: 10pt; font-family: verdana, helvetica, sans-serif; "> <div style="font-size: 12pt; font-family: 'times new roman', 'new york', times, serif; "> <div dir="ltr" style="font-family: 'times new roman', 'new york', times, serif; "> <font size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Jed Brown <jedbrown@mcs.anl.gov><br> <b><span style="font-weight: bold;">To:</span></b> Abdul Hanan Sheikh <hanangul12@yahoo.co.uk> <br><b><span style="font-weight: bold;">Cc:</span></b> PETSc users list <petsc-users@mcs.anl.gov> <br> <b><span
style="font-weight: bold;">Sent:</span></b> Thursday, 5 April 2012, 20:17<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [petsc-users] Implementation of Multilevel preconditioner<br> </font> </div> <br><div id="yiv886134242" style="font-family: 'times new roman', 'new york', times, serif; "><div class="yiv886134242gmail_quote">On Thu, Apr 5, 2012 at 11:12, Abdul Hanan Sheikh <span dir="ltr"><<a rel="nofollow" ymailto="mailto:hanangul12@yahoo.co.uk" target="_blank" href="mailto:hanangul12@yahoo.co.uk">hanangul12@yahoo.co.uk</a>></span> wrote:<br><blockquote class="yiv886134242gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div style="font-size: 10pt; font-family: verdana, helvetica, sans-serif; ">Recursive two level multigrid (by using PCMG with my desired stuff in it, in PCSHELL) is okay. I will do it recursively. <br>No Problem with recursion and nested iterations. <br>
Coming to two level, <br>How can I get exactly Prec = C + M^-1 (I - A*C) in a two level multigrid ? <br>What should be specific choice of pre_smoother_ksp_context and post_smoother_ksp_context <br>to get the "Prec" ? <br>
what operators should be chosen in these two ksp contexts ? </div></blockquote></div><br><div>This is just -pc_mg_type kaskade (zero pre-smoothing iterations, one post-smoothing iteration).</div>
</div><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255); ">Thanks. and cleared!</span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255); "><br></span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255); ">Post-smoothing context details would be appreciated! </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">To my understing, those would be: </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">1
post-smoothing iteration with </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">KSP type Richardson </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">PC type to be applied on M is PCShellForM (say there PCLU in PCShellForM, though I need to change this, so I say this) . </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);"><br></span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">This will complete my preconditioner
"Prec" ?? </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);"><br></span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">Bundle of thanks, </span></span></div><div style="font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><span style="font-family: verdana, helvetica, sans-serif;"><span style="color: rgb(0, 0, 255);">Abdul <br></span><br> </span></div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><br></div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; " class="yui_3_2_0_18_133364988655584"><br></div> </div> </blockquote></div> </div></body></html>