Topology optimization example in code gallery should use better use of topology

[KristofferC]

Ferrite.jl/docs/src/literate-gallery/topology_optimization.jl

Lines 194 to 216 in f7f2592

	function cache_neighborhood(dh, topology)
	nbgs = Vector{Vector{Int}}(undef, getncells(dh.grid))
	_nfacets = nfacets(dh.grid.cells[1])
	opp = Dict(1=>3, 2=>4, 3=>1, 4=>2)
	for element in CellIterator(dh)
	nbg = zeros(Int,_nfacets)
	i = cellid(element)
	for j in 1:_nfacets
	nbg_cellid = getneighborhood(topology, dh.grid, FacetIndex(i,j))
	if(!isempty(nbg_cellid))
	nbg[j] = first(nbg_cellid)[1] # assuming only one face neighbor per cell
	else # boundary face
	nbg[j] = first(getneighborhood(topology, dh.grid, FacetIndex(i,opp[j])))[1]
	end
	end
	nbgs[i] = nbg
	end
	return nbgs
	end
	#md nothing # hide

Some problems with this code:

• _nfacets = nfacets(dh.grid.cells[1])
• dh.grid is an implementation detail?
• opp could be a tuple
• It should use get_facet_facet_neighborhood instead (but this is undocumented?)