<html><body><div style="color:#000; background-color:#fff; font-family:verdana, helvetica, sans-serif;font-size:10pt"><div><span>Thanks for reply! <br></span></div><div><span>Well at first look, it looks like that M can be put as precondittioning operator for smoother</span></div><div><span>where keeping ksp as preonly in pre-smoother context. </span></div><div><span>I am not sure, this leads to the preconditioner desired, coz putting M as preconditioner in <br></span></div><div><span>pre-smoother alters the residual passed to coarse-grid correction, i.e. <br></span></div><div><span>CGC corrects the pre-smoothed solution. <br></span></div><div><br><span></span></div><br><div><span style="color:rgb(0, 0, 255);"><span style="font-family:verdana, helvetica, sans-serif;"><span style="font-family:lucida console, sans-serif;"></span></span></span><span style="color:rgb(0, 0, 255);"><span style="font-family:verdana, helvetica,
sans-serif;"></span></span></div><div><br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; margin-top: 5px; padding-left: 5px;"> <div style="font-family: verdana, helvetica, sans-serif; font-size: 10pt;"> <div style="font-family: times new roman, new york, times, serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> <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>; PETSc users list <petsc-users@mcs.anl.gov> <br><b><span style="font-weight: bold;">Cc:</span></b> Abdul - CITG <A.H.Sheikh@tudelft.nl> <br> <b><span style="font-weight: bold;">Sent:</span></b> Friday, 8 June 2012, 19:01<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [petsc-users] How to implement projection preconditioner?<br> </font> </div> <br><div
id="yiv1054561017">Isn't this just putting M and M_H as the preconditioning operator for the smoother?<br><br><div class="yiv1054561017gmail_quote">On Fri, Jun 8, 2012 at 11:58 AM, 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="yiv1054561017gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div><div style="font-size:10pt;font-family:verdana, helvetica, sans-serif;"><div><span>Dear all, <br></span></div><div><span>Summer greetings, <br>
</span></div><div><span>I am back with an other query.</span></div><div><span>Before I successfully implement the projection preconditioner which was simply <br></span></div><div><span>the coarse grid correction operator P = I - A*(P*A_H*R); <br>
</span></div><div><span>I implemented this simply keeping both pre and post smoothing dummy in PCMG setup. <br></span></div><div><span>Now I need to revise this and re-implement this where I replace A and coarse operator A_H with <br>
</span></div><div><span>preconditioned one i.e. M^-1 A and M^-1 A_H respectively. Thus new projection reads as</span></div><div><span> <br></span></div><div><br><span></span></div><div><span>P_new = I - (M^-1 A) {P*(M_H^-1 A_H)*R}</span></div>
<div><br><span></span></div><div><span>Any suggestion to
implement this in Petsc would be appreciated. <br></span></div><div><br><span></span></div><div><span>Thanking in anticipation. <br></span></div><div><span>with regards, Abdul <br></span></div><div><span style="color:rgb(0,0,255);"><span style="font-family:verdana, helvetica, sans-serif;"><span style="font-family:lucida console, sans-serif;"></span></span></span><span style="color:rgb(0,0,255);"><span style="font-family:verdana, helvetica, sans-serif;"></span></span></div>
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