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<div class="moz-cite-prefix">Hey Marcus,<br>
it's a long time since I last worked on nonoverlapping AMG...<br>
When I finished working on nonoverlapping AMG it was only possible
to use atOnceAccu or noAccu.<br>
(This is not too well documented, I know, in
novlpistlsolverbackend.hh there is this one line: //use noAccu or
atOnceAccu)<br>
<br>
The problem had something to do with the fact, that the owner
process of a vertex does not always know all neighbours of this
vertex.<br>
Therefore in matrixredistribute.hh there exists a function
completeSparsityPattern that adds missing entries for the
nonoverlapping case.<br>
Somehow this was problematic for the successiveAccu mode, but I
cannot remember the exact problem right now, sorry :-(.<br>
At this time atOnceAccu mode was enough for everyone so I did not
work further on it, but I think one would have to extend
matrixredistribute.hh from istl to use successiveAccu with
nonoverlapping AMG.<br>
<br>
If you want I can check tomorrow if I can find more in my notes...<br>
Bye,<br>
Rebecca<br>
<pre class="moz-signature" cols="72">--
Rebecca de Cuveland
Universität Heidelberg
Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Im Neuenheimer Feld 368, 69120 Heidelberg
Tel: 06221/548890 Fax: 06221/548884
e-mail: <a class="moz-txt-link-rfc2396E" href="mailto:rebecca.cuveland@iwr.uni-heidelberg.de"><rebecca.cuveland@iwr.uni-heidelberg.de></a> </pre>
On 04.09.2014 11:00, Markus Blatt wrote:<br>
</div>
<blockquote cite="mid:20140904090003.GA13372@boromir.dr-blatt.de"
type="cite">
<pre wrap="">Hi,
is there a special reason (e.g. a bug), why the default accumulation
mode for the nonoverlapping AMG ist atOnceAccu (if accumulation
happens, everything is gathered on one process)? For the overlapping
case we allow the numbers of processes on the coarse level to decrease
to a smaller number of processes (>=1) and do this successfully.
Markus
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