[Dune] Error in implementing PAAMG using dune-istl

Markus Blatt markus at dr-blatt.de
Thu Dec 14 15:39:10 CET 2017


Hi,

On Thu, Dec 14, 2017 at 02:44:14PM +0100, Markus Blatt wrote:
> On Thu, Dec 14, 2017 at 02:15:46PM +0100, Kumar, Paras wrote:
> > Another point is that for 2 process and 33 unknowns it shows,
> > 
> > Level 0 has 33 unknowns, 16.5 unknowns per proc (procs=2)
> > 
> > Probably, the distribution of indexes across processes is not happening
> > properly. Do I need to somehow ensure the linking of the Matrix index set to
> > the DuneComm object.
> 
> That looks distributed to me. Each process has about 16 unknowns. But
> maybe I misunderstood you?

On a second look. Somehow I cannot find any place where you distribute
your linear system. To me it looks like only rank 0 actually creates a
matrix with entries. All other ranks have a matrix with zero rows and
columns (which might not be well tested). In addition your index set
is empyty and the call to DuneComm.remoteIndices().template
rebuild<false>() will create no remote indices. So even if the
segfault is gone this will be a pure sequential solve.

Markus

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