Geometry, topology and tags

cmap

fenicsx_compat.cmap(mesh) -> dolfinx.fem.CoordinateElement

The coordinate element of the mesh geometry.

DOLFINx	Native
0.10	mesh.geometry.cmap
0.11, main	mesh.geometry.cmaps[0]. mesh.geometry.cmap still works but emits a DeprecationWarning.

cell = 0
nodes = mesh.geometry.x[fenicsx_compat.dofmap(mesh)[cell]]
X = fenicsx_compat.cmap(mesh).pull_back(np.array([[0.2, 0.1, 0.0]]), nodes)

dofmap

fenicsx_compat.dofmap(mesh) -> numpy.ndarray

The geometry dofmap: the node indices of each cell, shape (num_cells, num_nodes_per_cell).

DOLFINx	Native
0.10	mesh.geometry.dofmap
0.11, main	mesh.geometry.dofmaps[0]. mesh.geometry.dofmap still works but emits a DeprecationWarning.

cell_nodes = mesh.geometry.x[fenicsx_compat.dofmap(mesh)]  # (num_cells, num_nodes_per_cell, 3)

meshtags_topology

Added in version 0.2.0.

fenicsx_compat.meshtags_topology(tags) -> dolfinx.mesh.Topology

The topology a MeshTags is defined on, always as the Python dolfinx.mesh.Topology.

DOLFINx	tags.topology returns	Native Python topology
0.10, 0.11	the C++ topology	dolfinx.mesh.Topology(tags.topology)
main (DOLFINx PR #4350)	the Python topology	tags.topology

topology = fenicsx_compat.meshtags_topology(facet_tags)
cpp_topology = topology._cpp_object  # the C++ object, on every version

cell_permutation_info

fenicsx_compat.cell_permutation_info(topology) -> numpy.ndarray  # uint32

Computes and returns the packed per-cell permutation info, ghost cells included, as used by dof transformations.

DOLFINx	Native
0.10, 0.11	topology.create_entity_permutations(), then topology.get_cell_permutation_info()
main (DOLFINx PR #3904)	topology.create_cell_permutations(), then topology.get_cell_permutation_info(). create_entity_permutations now takes a dimension.

cell_info = fenicsx_compat.cell_permutation_info(mesh.topology)
# e.g. for V.element.Tt_inv_apply(data, cell_info, n)

Calling it is also the portable way to make sure the permutations are computed before handing the topology to code that needs them.

facet_permutations

fenicsx_compat.facet_permutations(topology) -> numpy.ndarray  # uint8

The permutation of every facet of every cell, shape (num_cells, num_facets_per_cell), ghost cells included. These are the values FFCx kernels take as quadrature_permutation.

DOLFINx	Native
0.10, 0.11	topology.create_entity_permutations(), then topology.get_facet_permutations(), which is flat
main (DOLFINx PR #3904)	topology.create_entity_permutations(tdim - 1), then topology.get_entity_permutations(tdim - 1), which is flat

perms = fenicsx_compat.facet_permutations(mesh.topology)
perm = perms[cell, local_facet]

On main, an interval mesh gives an empty array, since points have no orientation.

create_facet_orientations

Added in version 0.3.0.

fenicsx_compat.create_facet_orientations(topology) -> None

Computes the facet orientations that Raviart-Thomas and other contravariant Piola spaces need on a manifold. Call it on every rank, before creating the space.

DOLFINx	Native
0.10, 0.11	No equivalent, and none needed: such spaces are created without it. Does nothing.
main (DOLFINx PR #4625)	topology.create_facet_orientations(). Creating such a space on a manifold raises RuntimeError until it has been called.

submesh = dolfinx.mesh.create_submesh(mesh, 2, boundary_facets)[0]
fenicsx_compat.create_facet_orientations(submesh.topology)
V = dolfinx.fem.functionspace(submesh, ("RT", 1))

On main it raises ValueError for a topology whose dimension is not 2, as the native method does. Lagrange and Nédélec spaces do not need it.

transfer_meshtags_to_submesh

fenicsx_compat.transfer_meshtags_to_submesh(entity_tag, submesh, cell_to_parent, vertex_to_parent)
    -> dolfinx.mesh.MeshTags

Transfers tags on a parent mesh to a submesh created with dolfinx.mesh.create_submesh().

DOLFINx	Native
0.10	No equivalent. Raises NotImplementedError; scifem.transfer_meshtags_to_submesh() has a compiled implementation.
0.11	dolfinx.mesh.transfer_meshtags_to_submesh(entity_tag, submesh, vertex_to_parent, cell_to_parent)
main	dolfinx.mesh.transfer_meshtags_to_submesh(entity_tag, submesh, cell_to_parent, vertex_to_parent)

The two maps swapped places between 0.11 and main while keeping their names, so a positional call that is right on one version passes the maps the wrong way round on the other. That does not raise. The wrapper forwards by keyword, and takes the maps in the order create_submesh returns them:

submesh, cell_map, vertex_map, _ = dolfinx.mesh.create_submesh(mesh, tdim, cells)
sub_tags = fenicsx_compat.transfer_meshtags_to_submesh(cell_tags, submesh, cell_map, vertex_map)

If you call DOLFINx directly, pass both maps by keyword: cell_to_parent=cell_map, vertex_to_parent=vertex_map.