<div dir="ltr"><div><div><div>Hello Dion,<br><br></div><div>while at first glance, I was inclined to say that this has something to do with the fact that your solution vector is fitting the L1 Cache in the smaller test and does not in the bigger, I am not so sure now. That does not explain a breakdown of the linear solver. For further analysis, we would need to investigate your local operator, your build system flags and so on. To speed things up: What do you think about just coming over some time today and analyze it on site (to call me, dial 8888)? Might as well use the fact we are working on the same campus. Dont worry mailing list: We will give you a summary afterwards!<br><br></div><div>Dominic<br></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Jan 22, 2015 at 10:02 AM, Dion Häfner <span dir="ltr"><<a href="mailto:dhaefner@iup.uni-heidelberg.de" target="_blank">dhaefner@iup.uni-heidelberg.de</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">
Hey Dominic,<br>
<br>
thank you for your answer. I am solving the Richards Equation
(nonlinear PDE) with the DG method, essentially using:<br>
<br>
typedef
Dune::PDELab::QkDGLocalFiniteElementMap<Real,Real,order,dim>
FEM; as finite element map,<br>
typedef Dune::PDELab::ISTLBackend_BCGS_AMG_SSOR<IGO> LS;
as linear solver,<br>
typedef Dune::PDELab::Newton<IGO,LS,U> PDESOLVER; as
non-linear solver,<br>
Dune::PDELab::Alexander2Parameter<Real> alex2; as
timestepper.<br>
<br>
The grid is set up with<br>
<br>
Dune::FieldVector<double,dim> N;<br>
for (unsigned int i=0; i<dim; i++)<br>
N[i] = elements[i]; <br>
Dune::FieldVector<bool,dim> periodic(false);<br>
int overlap = 2;<br>
const YaspXDirPartition<dim> yp;<br>
Dune::YaspGrid<dim>
grid(helper.getCommunicator(),upperRight,N,periodic,overlap,&yp);<br>
typedef Dune::YaspGrid<dim>::LeafGridView GV;<br>
const GV& gv=grid.leafGridView();<br>
<br>
I have appended the source code responsible for the actual solution,
along with two logfiles - one with barely over 2000 elements in the
grid, one barely below. You can see that the amount of linear
iterations (and thus linear solve time) rises sharply if the
elements exceed 2000.<br>
<br>
I hope this is enough information to address this problem - if not,
please tell me so.<br>
<br>
<br>
Thank you kindly for your time!<br>
<br>
Dion<br>
<br>
<br>
<div>Am 21.01.15 um 10:23 schrieb Dominic
Kempf:<br>
</div><div><div class="h5">
<blockquote type="cite">
<div dir="ltr">
<div>
<div>Hello Dion,<br>
<br>
</div>
to answer your question we need some information on the exact
problem you are using for this benchmark. Can you provide us
the code? I will refrain from any wild guesses that come to my
mind before having seen the actual problem.<br>
<br>
</div>
Best,<br>
Dominic<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Jan 20, 2015 at 7:33 PM, Dion
Häfner <span dir="ltr"><<a href="mailto:dhaefner@iup.uni-heidelberg.de" target="_blank">dhaefner@iup.uni-heidelberg.de</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear
PDELab Developers,<br>
<br>
when I was benchmarking my DUNE / PDELab module, I noticed a
sudden jump in runtime (approx. by a factor of 4) as soon as
the number of grid elements exceeded 2000 in a YaspCube
grid. I could not reproduce this behavior with UG Grids, so
I think it is somewhat specific to YaspCube Grids.<br>
<br>
Has anyone encountered a similar behavior before? How can
this be adressed?<br>
<br>
Sorry if my question is not very specific. If you need
further information on my module or the methods used, please
ask and I will provide.<br>
<br>
Thank you in advance,<br>
<br>
Dion Häfner<br>
<br>
_______________________________________________<br>
dune-pdelab mailing list<br>
<a href="mailto:dune-pdelab@dune-project.org" target="_blank">dune-pdelab@dune-project.org</a><br>
<a href="http://lists.dune-project.org/mailman/listinfo/dune-pdelab" target="_blank">http://lists.dune-project.org/mailman/listinfo/dune-pdelab</a><br>
</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div></div></div>
<br>_______________________________________________<br>
dune-pdelab mailing list<br>
<a href="mailto:dune-pdelab@dune-project.org">dune-pdelab@dune-project.org</a><br>
<a href="http://lists.dune-project.org/mailman/listinfo/dune-pdelab" target="_blank">http://lists.dune-project.org/mailman/listinfo/dune-pdelab</a><br>
<br></blockquote></div><br></div>