<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">If your machine can "scale" a dot product then it can scale AMG. That said, implementing AMG to scale well takes work. GAMG should be able to go to 10^4 processes. We are working on some scaling problems in the setup code and I'm not too sure what and where GAMG will break as you scale up. I'd be curious to know. hypre should scale pretty well.<div><br></div><div><br><div><div>On Nov 9, 2012, at 12:43 PM, Thomas Witkowski <<a href="mailto:Thomas.Witkowski@tu-dresden.de">Thomas.Witkowski@tu-dresden.de</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div class="moz-cite-prefix">:) It was just a question whether is
makes sense to run my solver in this range of number of cores, or
whether AMG by itself will not scale here anymore. As my
computational time is limited, I have to think carefully when
using 10^4 cores.<br>
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Thomas<br>
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Am 09.11.2012 18:40, schrieb Jed Brown:<br>
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<div class="gmail_extra">Don't speculate, send -log_summary and
information about the problem and machine. Some setup operations
degrade, but solves should scale pretty well.<br>
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<div class="gmail_quote">On Fri, Nov 9, 2012 at 11:37 AM, Thomas
Witkowski <span dir="ltr"><<a moz-do-not-send="true" href="mailto:thomas.witkowski@tu-dresden.de" target="_blank">thomas.witkowski@tu-dresden.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">While
we're at it, can some of you tell me some world about
parallel scaling of algebraic multigrid methods? In most of
my codes I use them to precondition some simple blocks, e.g.
Laplace matrix. I'm pretty sure that parallel scaling of my
solver is limited mostly by scaling of the AMG method which
is used. What are the expectations, when going to 10^3 or
10^4 cores?</blockquote>
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