You can get this effect using PCBJACOBI, setting the number of local blocks, and using -sub_pc_type lu -sub_ksp_type preonly.<div><br></div><div> Matt<br><br><div class="gmail_quote">On Thu, Dec 1, 2011 at 4:28 AM, Parker, Andrew (UK Filton) <span dir="ltr"><<a href="mailto:Andrew.Parker2@baesystems.com">Andrew.Parker2@baesystems.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div lang="EN-GB" link="blue" vlink="purple"><div><p class="MsoNormal">Hi,<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">I’ve been using PETSc for a conventional full parallel implicit solver, currently in MPIBAIJ format. However, I’d like to understand the performance verse memory and speed trade-offs of just having a block diagonal system. In this case I do not scatter to the off diagonal blocks. Each block is 7x7 in size and fully dense. In my view this should be a point implicit solution of the system. I am looking for the best way to solve this in PETSc, clearly because of the lack of coupling between neighbouring cells by only having a block diagonal it’s actually a 7x7 dense linear solve, but to test my theory at present I’d prefer to just not scatter to off diagonals, and use:<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">MATBDIAG with my current ksp solver and take it from there. BDIAG seems to have been removed as off 3.0:<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><a href="http://www.mcs.anl.gov/petsc/documentation/changes/300.html" target="_blank">http://www.mcs.anl.gov/petsc/documentation/changes/300.html</a><u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Can anybody help me with this, your thoughts on the above and what I should use to solve this reduced system would be appreciated??<u></u><u></u></p><p class="MsoNormal"><br>Cheers,<u></u><u></u></p><p class="MsoNormal">
Andy<u></u><u></u></p></div> <br>
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</div></blockquote></div><br><br clear="all"><div><br></div>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
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