#use wml::std::lang
#use wml::fmt::isolatin

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#include <banner.wml>  title="Research" path="research"

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<li> a list of my <a href="publications.html">publications</a>
(journals, conference's articles and freely available research reports)
<li> some material from the <a href="talks.html">talks</a> I have given


<frame title="Out-of-core solution for sparse direct methods">
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<h3>Motivations and Principles</h3>

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  The memory usage of sparse direct solvers can be the bottleneck to
  solve large-scale problems. The out-of-core approach consists in
  extending the core memory by disks. 
<a href="Img/tomography_large.jpg"><img align=top border=0 src="Img/tomography_large.jpg" alt="" width="200" height="200"></a>


  We have developed a prototype of an out-of-core extension to a
  parallel multifrontal solver 
  (<a href="http://graal.ens-lyon.fr/MUMPS/">MUMPS</a>). We show that,
  by storing the factors to disk, larger problems can be solved on 
  limited-memory machines with reasonable performance (see <a href="publications.html#agul:06">article in EuroPar'06</a>).
  We have illustrated the impact of low-level IO mechanisms on the
  behaviour of our parallel out-of-core factorization. Then have used simulations
  to discuss how our algorithms can be modified to solve much
  larger problems at the cost of increasing the volume of disk access
  (see <a href="publications.html#agul:06b">article in RenPar'06</a>).