<div dir="ltr"><div class="markdown-here-wrapper" style="font-family:'Courier New'"><p style="margin:1.2em 0px!important">Hello all,</p>
<p style="margin:1.2em 0px!important">I want to solve the following system [1]<br> ∇ × 1/μ  ∇ × u + ∇ P = f<br> ∇ ⋅ u = 0<br>with μ​ = cst.</p>
<p style="margin:1.2em 0px!important">This produce, in the preconditioner, two systems to solve. The first one is related to AMS (with a non null β​), the second one is a laplacian.</p>
<p style="margin:1.2em 0px!important">I use <a href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCHYPRE.html"><strong>Hypre/Ams</strong></a> as a preconditioner to solve the first system.</p>
<p style="margin:1.2em 0px!important">I have verified my implementation to solve the full problem in sequential, using the default parameters, on 3D academic test cases. I obtain the second order accuracy as expected.</p>
<p style="margin:1.2em 0px!important">On <strong>some</strong> parallel cases, the solver related to the first system (after few iterations) does not converge (Indefinite matrix or Indefinite preconditioner). If I generate [2] - from the same mesh - a new partitionning, I can obtain convergence (but that is not always true)<br>I have implemented my own version of the ams preconditioner following [1] and the system (slowly) converge.<br>I use {Hypre-AMS OR my own implementation}/CG to solve the corresponding system.<br>If I switch from hypre-ams/CG to hypre-ams/gmres, then I obtain - at least for that case - convergence.<br>If I use my own implementation/CG, then I obtain - at least for that case - convergence (but that is very slow !) </p>
<p style="margin:1.2em 0px!important">My questions are: </p>
<ul style="margin:1.2em 0px;padding-left:2em">
<li style="margin:0.2em 0px">why does the hypre-ams preconditioner loose the SDP property ? </li>
<li style="margin:0.2em 0px">Do I miss anything else ?</li>
</ul>
<p style="margin:1.2em 0px!important">I have tried various <code style="font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:inherit;line-height:inherit;font-family:inherit;margin:0px 0.15em;padding:0px 0.15em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">cycle-type</code> and smoothing options in the hypre-ams preconditioner with CG without success.</p>
<p style="margin:1.2em 0px!important">Vincent H</p>
<p style="margin:1.2em 0px!important">[1]For more details, see  <em>Parallel numerical solution of the time-harmonic Maxwell equations in mixed form</em><br>[2] <code style="font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:inherit;line-height:inherit;font-family:inherit;margin:0px 0.15em;padding:0px 0.15em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">gmsh my.msh -3 -part n -o new.msh</code></p>
<p style="margin:1.2em 0px!important">–<br>Docteur Ingénieur de recherche<a href="http://www.cemosis.fr">CeMoSiS</a> - <a href="mailto:vincent.huber@cemosis.fr">vincent.huber@cemosis.fr</a><br>Tel: +33 (0)3 68 85 02 06<br>IRMA - 7, rue René Descartes<br>67 000 Strasbourg</p>
<p style="margin:1.2em 0px!important"><img src="http://www.google.com/a/cpanel/cemosis.fr/images/logo.gif"></p>
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