DOLFIN User Manual - FEniCS Project

Chapter 4The mesh◮ Developer’s note: This chapter is currently being written. . .The concept of a mesh is central in the implementation of adaptive Galerkinfinite element methods for partial differential equations. Related importantconcepts include vertices, cells, edges, faces, boundaries, and mesh hierarchies.These concepts are all implemented as C++ classes in DOLFIN, asshown in Figure 4.1.4.1 Mesh iteratorsAlgorithms operating on a mesh, including adaptive mesh refinement, canoften be expressed in terms of iterators, i.e., objects used for the traversal ofaggregate structures, such as the list of vertices contained in a mesh. Iteratorsimplemented in DOLFIN include a VertexIterator, CellIterator,EdgeIterator, FaceIterator, and a MeshIterator. The following code illustrateshow to iterate over all vertex neighbors of all vertices of all cellswithin a given mesh:29