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Keep a consistent labeling of boundaries for 2D periodic meshes #5005

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Keep a consistent labeling of boundaries for 2D periodic meshes #5005

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ae95f93
Keep a consistent labeling of boundaries for 2D periodic meshes
connorjward Mar 31, 2026
bd1312c
Update tests/firedrake/regression/test_periodic_2d.py
connorjward Apr 1, 2026
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connorjward Apr 1, 2026
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130 changes: 58 additions & 72 deletions firedrake/utility_meshes.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
import numbers
import numpy as np
import warnings
from collections.abc import Mapping
from typing import Literal

import petsctools
Expand Down Expand Up @@ -929,36 +928,29 @@ def PeriodicRectangleMesh(
Notes
-----

If direction == "x" the boundary edges in this mesh are numbered as follows:

* 1: plane y == 0
* 2: plane y == Ly

If direction == "y" the boundary edges are:
The boundary edges in this mesh are numbered as follows:

* 1: plane x == 0
* 2: plane x == Lx
* 3: plane y == 0
* 4: plane y == Ly

If periodic in the 'x' direction then boundary edges 1 and 2 are empty, and
if periodic in 'y' then 3 and 4 are empty.

"""
if quadrilateral and diagonal is not None:
raise ValueError("Cannot specify slope of diagonal on quad meshes")
if not quadrilateral and diagonal is None:
diagonal = "left"

# TODO: Remove this awkward mapping, this will be a breaking API change
# for which a deprecation policy cannot be followed
plex_to_firedrake_boundary_labels = None
match direction:
case "both":
periodic = (True, True)
case "x":
periodic = (True, False)
# NOTE: The vertical faces (plex faces 2 and 4) have arbitrary
# labels. What matters is that we have 1->1 and 3->2.
plex_to_firedrake_boundary_labels = {1: 1, 2: 4, 3: 2, 4: 3}
case "y":
periodic = (False, True)
# default plex to firedrake label mapping is correct
case _:
raise ValueError(
f"Cannot have a periodic mesh with periodicity '{direction}'"
Expand All @@ -974,7 +966,7 @@ def PeriodicRectangleMesh(
sparseLocalize=False,
comm=comm
)
_mark_mesh_boundaries(plex, plex_to_firedrake_boundary_labels)
_mark_mesh_boundaries(plex)
if not quadrilateral:
plex = _refine_quads_to_triangles(plex, diagonal)

Expand Down Expand Up @@ -1043,16 +1035,16 @@ def PeriodicSquareMesh(

Notes
-----
If direction == "x" the boundary edges in this mesh are numbered as follows:

* 1: plane y == 0
* 2: plane y == L

If direction == "y" the boundary edges are:
The boundary edges in this mesh are numbered as follows:

* 1: plane x == 0
* 2: plane x == L
* 3: plane y == 0
* 4: plane y == L

If periodic in the 'x' direction then boundary edges 1 and 2 are empty, and
if periodic in 'y' then 3 and 4 are empty.
"""
return PeriodicRectangleMesh(
nx,
Expand Down Expand Up @@ -1122,16 +1114,16 @@ def PeriodicUnitSquareMesh(

Notes
-----
If direction == "x" the boundary edges in this mesh are numbered as follows:

* 1: plane y == 0
* 2: plane y == 1

If direction == "y" the boundary edges are:
The boundary edges in this mesh are numbered as follows:

* 1: plane x == 0
* 2: plane x == 1
* 3: plane y == 0
* 4: plane y == 1

If periodic in the 'x' direction then boundary edges 1 and 2 are empty, and
if periodic in 'y' then 3 and 4 are empty.
"""
return PeriodicSquareMesh(
nx,
Expand Down Expand Up @@ -3091,54 +3083,48 @@ def PartiallyPeriodicRectangleMesh(
)


def _mark_mesh_boundaries(
plex: PETSc.DMPlex,
plex_to_firedrake_boundary_labels: Mapping[int, int] | None = None,
) -> None:
def _mark_mesh_boundaries(plex: PETSc.DMPlex) -> None:
"""Reorder the 'Face Sets' label of the DMPlex to match Firedrake ordering."""
# TODO: Remove the awkward face set mapping for 2D periodic domains

if plex_to_firedrake_boundary_labels is None:
match plex.getDimension():
case 0:
plex_to_firedrake_boundary_labels = {}
case 1:
# Firedrake and DMPlex conventions agree (left is 1, right is 2)
plex_to_firedrake_boundary_labels = {1: 1, 2: 2}
case 2:
# DMPlex Firedrake
#
# 3 4
# +-----+ +-----+
# | | | |
# 4| |2 1| |2
# | | | |
# +-----+ +-----+
# 1 3
plex_to_firedrake_boundary_labels = {1: 3, 2: 2, 3: 4, 4: 1}
case 3:
# DMPlex Firedrake
#
# +-------+ +-------+
# / /| / /|
# / / | / / |
# / 4/3 / | / 4/3 / |
# / / | / / |
# / / | / / |
# +-------+ 5/6 + +-------+ 2/1 +
# | | / | | /
# | | / | | /
# y | 1/2 | / z y | 5/6 | / z
# | | / | | /
# | |/ | |/
# +-------+ +-------+
# O x O x
#
# 'x/y' means that 'x' is the label for the visible face and 'y'
# the label for the opposite hidden face.
plex_to_firedrake_boundary_labels = {1: 5, 2: 6, 3: 3, 4: 4, 5: 2, 6: 1}
case _:
raise AssertionError
match plex.getDimension():
case 0:
plex_to_firedrake_boundary_labels = {}
case 1:
# Firedrake and DMPlex conventions agree (left is 1, right is 2)
plex_to_firedrake_boundary_labels = {1: 1, 2: 2}
case 2:
# DMPlex Firedrake
#
# 3 4
# +-----+ +-----+
# | | | |
# 4| |2 1| |2
# | | | |
# +-----+ +-----+
# 1 3
plex_to_firedrake_boundary_labels = {1: 3, 2: 2, 3: 4, 4: 1}
case 3:
# DMPlex Firedrake
#
# +-------+ +-------+
# / /| / /|
# / / | / / |
# / 4/3 / | / 4/3 / |
# / / | / / |
# / / | / / |
# +-------+ 5/6 + +-------+ 2/1 +
# | | / | | /
# | | / | | /
# y | 1/2 | / z y | 5/6 | / z
# | | / | | /
# | |/ | |/
# +-------+ +-------+
# O x O x
#
# 'x/y' means that 'x' is the label for the visible face and 'y'
# the label for the opposite hidden face.
plex_to_firedrake_boundary_labels = {1: 5, 2: 6, 3: 3, 4: 4, 5: 2, 6: 1}
case _:
raise AssertionError

# Get the original label
plex_boundary_label = plex.getLabel(dmcommon.FACE_SETS_LABEL)
Expand Down
3 changes: 1 addition & 2 deletions tests/firedrake/regression/test_periodic_2d.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,9 +38,8 @@

f = Function(V).assign((244.0*pi*pi/225.0 + 1.0)*u_exact)

if direction in {"x", "y"}:
bcs = DirichletBC(V, Constant(0), (1, 2))
bcs = DirichletBC(V, 0, "on_boundary")
elif direction == "both":

Check failure on line 42 in tests/firedrake/regression/test_periodic_2d.py

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E999 

tests/firedrake/regression/test_periodic_2d.py:42:6: E999 SyntaxError: invalid syntax
bcs = []
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u = TrialFunction(V)
v = TestFunction(V)
Expand Down
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