<div class="gmail_quote">On Fri, Mar 9, 2012 at 05:16, Abdul Hanan Sheikh <span dir="ltr"><<a href="mailto:hanangul12@yahoo.co.uk">hanangul12@yahoo.co.uk</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div style="color:#000;background-color:#fff;font-family:verdana,helvetica,sans-serif;font-size:10pt"><div><span>Dear, </span></div><div><br><span></span></div><div><span>To my earlier querry: <br></span></div><div class="im">
<div><br><span></span></div><blockquote style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div>What if I want to approximate my all coarse matrices with any Krylov iteration ?</div></blockquote></div><div>
reply: <br></div><div class="im"><div>The methods on each
level are independent, you can set them with -mg_coarse_ksp_type gmres
-mg_levels_1_ksp_type cg -mg_levels_1_ksp_max_it 100
-mg_levels_2_ksp_type minres ... <br></div></div><div> <br>This command line option changes the ksp_type on both ksp_pre and ksp_post (pre and post smoothing) . <br>Where as I need to fix the ksp_post_type as RICHARDSON to get my Prec = C + I - AC ; <br>
</div></div></div></blockquote><div><br></div><div>Do you want this on every level or still just the finest?</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div style="color:#000;background-color:#fff;font-family:verdana,helvetica,sans-serif;font-size:10pt"><div><br>If adapt pre_smoother as follows : <br><br>ierr = MGGetSmootherDown(pcmg,lev,&ksp_pre); CHKERRQ(ierr); <br>
</div>ierr = KSPSetType(ksp_pre, KSPGMRES);CHKERRQ(ierr);<br><br>Does ONLY setting pre_smoother as GMRES means that GMRES iterates on coarse matrix at level = lev ? <br></div></div></blockquote><div><br></div><div>Yes, this will only affect the pre-smoother (so it will then go to the next coarser grid, come back, and do a post-smoother). You may have to increase the number of iterations. I strongly recommend configuring the solver using the command line and checking that it is the method you intended by reading the output of -ksp_view.</div>
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