[Dune] erradic behaviour of parallel grid sizes in 3D

[Michael Wenske]

Dear list,

i am working on verifying a dune-pdelab code and most things work out
nifty.
To verify convergence and tackle possible weighting errors I chose
'ugly' Grid dimensions for a YaspGrid:

for example:

LX = 3.14159265359
LY = 1.41421356237
LZ =2.71828182845904523536028

NX = 15
Ny = 7
NZ =  13

Now the odd thing is that the code behaves nicely for some values of
NX/NY/NZ and gives the following errors (all MPI related)
for other values (namely the above).

command: mpirun -n 2 ./executable

*** Process received signal ***
Signal: Segmentation fault (11)
Signal code: Address not mapped (1)
 Failing at address: 0xffffffaa060feb70
[ 0] /lib/x86_64-linux-gnu/libpthread.so.0(+0x11390)[0x7f172f284390]
[ 1] /usr/local/lib/openmpi/mca_btl_vader.so(+0x405d)[0x7f17201a505d]
[ 2] /usr/local/lib/libopen-pal.so.20(opal_progress+0x3c)[0x7f172c113efc]
[ 3]
/usr/local/lib/libmpi.so.20(ompi_request_default_test+0x2a)[0x7f172fd7b72a]
[ 4] /usr/local/lib/libmpi.so.20(PMPI_Test+0x59)[0x7f172fdaaf49]
[ 5]
./dune-micro(_ZNK4Dune5TorusINS_23CollectiveCommunicationIP19ompi_communicator_tEELi3EE8exchangeEv+0x5ce)[0x96b3ea]

To root out any overflow error I chose a couple of settings with high
NX/NY/NZ and those work fine.
I may also chose grid dimensions with 2:1 aspect ratios. The error does
not seem to occur in 2D.

The grid instantiation looks like this, with overlap =1;

            typedef Dune::YaspGrid<3> Grid;
            typedef Grid::ctype DF;
            Dune::FieldVector<DF, dim> L;
            L[0] = ptree.get("grid.structured.LX", (double) 1.0);
            L[1] = ptree.get("grid.structured.LY", (double) 1.0);
            L[2] = ptree.get("grid.structured.LZ", (double) 1.0);
            std::array<int, dim> N;
            N[0] = ptree.get("grid.structured.NX", (int) 1);
            N[1] = ptree.get("grid.structured.NY", (int) 1);
            N[2] = ptree.get("grid.structured.NZ", (int) 1);
            int overlap = ptree.get<int>("grid.overlap", -1);       
//make it fail if unspecified
            std::bitset < dim > B(false);
            std::shared_ptr<Grid> gridp = std::shared_ptr < Grid > (new
Grid(L, N,B,overlap,Dune::MPIHelper::getCollectiveCommunication()));

I figured that this might also influence other peoples work. Are there
some restrictions on the Grid dimensions in Yasp grid for 3D, like only
2^n or sth.?
Is there anything else I have to consider when working with parallel grids?

Any hints are welcome,

Michael