void LaplaceMeshSmoother::init()
{
switch (_mesh.mesh_dimension())
{
// TODO:[BSK] Fix this to work for refined meshes... I think
// the implementation was done quickly for Damien, who did not have
// refined grids. Fix it here and in the original Mesh member.
case 2: // Stolen directly from build_L_graph in mesh_base.C
{
// Initialize space in the graph. It is indexed by node id.
// Each node may be connected to an arbitrary number of other
// nodes via edges.
_graph.resize(_mesh.max_node_id());
MeshBase::element_iterator el = _mesh.active_local_elements_begin();
const MeshBase::element_iterator end = _mesh.active_local_elements_end();
for (; el != end; ++el)
{
// Constant handle for the element
const Elem * elem = *el;
for (unsigned int s=0; s<elem->n_neighbors(); s++)
{
// Only operate on sides which are on the
// boundary or for which the current element's
// id is greater than its neighbor's.
// Sides get only built once.
if ((elem->neighbor(s) == libmesh_nullptr) ||
(elem->id() > elem->neighbor(s)->id()))
{
UniquePtr<Elem> side(elem->build_side(s));
_graph[side->node_id(0)].push_back(side->node_id(1));
_graph[side->node_id(1)].push_back(side->node_id(0));
}
}
}
_initialized = true;
break;
} // case 2
case 3: // Stolen blatantly from build_L_graph in mesh_base.C
{
// Initialize space in the graph.
_graph.resize(_mesh.max_node_id());
MeshBase::element_iterator el = _mesh.active_local_elements_begin();
const MeshBase::element_iterator end = _mesh.active_local_elements_end();
for (; el != end; ++el)
{
// Shortcut notation for simplicity
const Elem * elem = *el;
for (unsigned int f=0; f<elem->n_neighbors(); f++) // Loop over faces
if ((elem->neighbor(f) == libmesh_nullptr) ||
(elem->id() > elem->neighbor(f)->id()))
{
// We need a full (i.e. non-proxy) element for the face, since we will
// be looking at its sides as well!
UniquePtr<Elem> face = elem->build_side(f, /*proxy=*/false);
for (unsigned int s=0; s<face->n_neighbors(); s++) // Loop over face's edges
{
// Here we can use a proxy
UniquePtr<Elem> side = face->build_side(s);
// At this point, we just insert the node numbers
// again. At the end we'll call sort and unique
// to make sure there are no duplicates
_graph[side->node_id(0)].push_back(side->node_id(1));
_graph[side->node_id(1)].push_back(side->node_id(0));
}
}
}
_initialized = true;
break;
} // case 3
default:
libmesh_error_msg("At this time it is not possible to smooth a dimension " << _mesh.mesh_dimension() << "mesh. Aborting...");
}
// Done building graph from local elements. Let's now allgather the
// graph so that it is available on all processors for the actual
// smoothing operation?
this->allgather_graph();
// In 3D, it's possible for > 2 processor partitions to meet
// at a single edge, while in 2D only 2 processor partitions
// share an edge. Therefore the allgather'd graph in 3D may
// now have duplicate entries and we need to remove them so
// they don't foul up the averaging algorithm employed by the
// Laplace smoother.
for (unsigned i=0; i<_graph.size(); ++i)
{
// The std::unique algorithm removes duplicate *consecutive* elements from a range,
// so it only makes sense to call it on a sorted range...
std::sort(_graph[i].begin(), _graph[i].end());
_graph[i].erase(std::unique(_graph[i].begin(), _graph[i].end()), _graph[i].end());
}
} // init()
