<div class="gmail_quote">On Mon, Jan 9, 2012 at 13:11, TAY wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com">zonexo@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">Can you explain a bit more about how to adjust the subdomain aspect
ratios so that strongly coupled cells tend to reside on the same
process?</div></blockquote><div><br></div><div>You can set the lx,ly,lz in DMDACreate3d().</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
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<div bgcolor="#FFFFFF" text="#000000"> using fractional mtd
which solves the momentum and Poisson eqns. I construct the
linear eqn matrix and insert them in PETSc matrix/vectors.
Then I solve using Bicsstab and hypre AMG respectively. Why
is PCSetUp() and PCApply using more time?</div>
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<div>It is expensive because BoomerAMG setup and apply is
expensive.</div>
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So this is normal? Is there any suggestion to improve performance?</div></blockquote></div><br><div>This is normal for BoomerAMG. You could use PCGAMG (-pc_type gamg, better with petsc-dev) or ML (--download-ml, then -pc_type ml) which are algebraic multigrid methods that are usually less expensive to setup and per iteration (but sometimes less strong). Geometric multigrid is another possibility.</div>