Add hacky MPI support for grid refinement

Works but is nowhere near anything one could consider good.
Obvious issues:

* More than one cuboid per grid makes it harder to determine the next lattice cell to be coupled
	* i.e. currently lattice positions are determined ad hoc by resolving their physical position
* Coupling is not actually parallelized
	* All coupling lines are traversed by all processes, way to much communication
* Load balancing and cuboid decomposition doesn't care about refinement
	* ideally refined cuboids should be computationally near their coarse _parent_ cuboids

The first two isses should be fixable with a reasonable amount of work.
This sadly doesn't apply in any form to the last issue.

1 files changed, 7 insertions, 6 deletions

diff --git a/apps/adrian/poiseuille2d/poiseuille2d.cpp b/apps/adrian/poiseuille2d/poiseuille2d.cpp
index a6d7bd1..df166e1 100644
--- a/apps/adrian/poiseuille2d/poiseuille2d.cpp
+++ b/apps/adrian/poiseuille2d/poiseuille2d.cpp
@@ -35,10 +35,11 @@ typedef double T;
 
 #define DESCRIPTOR D2Q9Descriptor
 
-const T lx  = 4.0;            // length of the channel
-const T ly  = 1.0;            // height of the channel
-const int N = 60;             // resolution of the model
+const T lx  = 8.0;            // length of the channel
+const T ly  = 2.0;            // height of the channel
+const int N = 64;             // resolution of the model
 const T Re  = 500.;           // Reynolds number
+const T baseTau = 0.57;       // Relaxation time of coarsest grid
 const T maxPhysT = 60.;       // max. simulation time in s, SI unit
 const T physInterval = 0.25;  // interval for the convergence check in s
 const T residuum = 1e-5;      // residuum for the convergence check
@@ -183,10 +184,10 @@ int main(int argc, char* argv[])
   const Vector<T,2> coarseExtend {lx, ly};
   IndicatorCuboid2D<T> coarseCuboid(coarseExtend, coarseOrigin);
 
-  auto coarseGrid = Grid2D<T,DESCRIPTOR>::make(coarseCuboid, N, 0.57, Re);
+  auto coarseGrid = Grid2D<T,DESCRIPTOR>::make(coarseCuboid, N, baseTau, Re);
   prepareGeometry(coarseGrid->getConverter(), coarseGrid->getSuperGeometry());
 
-  const Vector<T,2> wantedFineExtend {2.0, 0.75};
+  const Vector<T,2> wantedFineExtend {3.0, 1.5};
   const Vector<T,2> fineOrigin = coarseGrid->alignToGrid({0.8, (ly-wantedFineExtend[1])/2});
   const Vector<T,2> fineExtend = coarseGrid->alignToGrid(fineOrigin + wantedFineExtend) - fineOrigin;
 
@@ -220,7 +221,7 @@ int main(int argc, char* argv[])
   sOnLatticeBoundaryCondition2D<T, DESCRIPTOR> fineSBoundaryCondition(fineGrid->getSuperLattice());
   createLocalBoundaryCondition2D<T, DESCRIPTOR>(fineSBoundaryCondition);
 
-  const Vector<T,2> wantedFineExtend2 {0.4, 0.4};
+  const Vector<T,2> wantedFineExtend2 {0.6, 0.4};
   const Vector<T,2> fineOrigin2 = fineGrid->alignToGrid({1.05, (ly-wantedFineExtend2[1])/2});
   const Vector<T,2> fineExtend2 = fineGrid->alignToGrid(fineOrigin2 + wantedFineExtend2) - fineOrigin2;