from functools import partial
import numpy as np
from cached_property import cached_property
import dolfin
from .product2d import Product2DMesh
from .mesh1d import make_1d_mesh_from_points
__all__ = [
'clip_intervals',
'Interval', 'CInterval', 'GeometricallyExpandingMeshInterval',
'Product2DMeshMixin', 'Interval1DMesh', 'Interval1DMeshMixin',
'MinimumCoordinateDistanceMixin',
'BaseInterval1DTag', 'Interval1DTag']
[docs]
def clip_intervals(x0, x1, intervals):
''' in-place modifies intervals '''
for I in intervals:
I.x0 = max(I.x0, x0)
I.x1 = min(I.x1, x1)
new = [I for I in intervals
if I.x0 != I.x1] # remove degenerate intervals
intervals[:] = new
return intervals
[docs]
class Interval(object):
''' Represents a single interval, possibly with tags. '''
def __init__(self, x0, x1, tags=()):
self.x0 = x0
self.x1 = x1
self.tags = frozenset(tags)
def __repr__(self):
return "{}(x0={}, x1={}{})".format(self.__class__.__name__,
self.x0, self.x1,
self._supplementary_repr())
def _supplementary_repr(self):
return ', tags={{{}}}'.format(', '.join(repr(t) for t in self.tags))
[docs]
class CInterval(Interval):
''' Represents an interval with constant edge length (in the x
direction).
Note: you do not need to derive from this class to implement a
custom edge length. Instead, you can subclass from
:py:class:`Interval` and implement a custom
:code:`local_edge_length` method. '''
def __init__(self, x0, x1, tags=(), edge_length=np.inf):
self.edge_length = edge_length
super().__init__(x0, x1, tags)
[docs]
def local_edge_length(self, x):
return self.edge_length
def _supplementary_repr(self):
return '{}, edge_length={!r}'.format(
super()._supplementary_repr(), self.edge_length)
[docs]
class GeometricallyExpandingMeshInterval(Interval):
"""
Interval of 1D mesh where the edge lengths start at ``start`` and
increase geometrically away from the region bounds.
See ``doc/mesh.lyx`` for more information.
(Local edge length: minimum distance between two mesh vertices.)
Parameters
----------
bounds: tuple
Tuple defining the region.
edge_length_start: float or tuple
The initial edge length at the bounds. To have different
initial edge lengths at the two ends of the region, pass in a
tuple.
edge_length_expansion_factor: float or tuple
Geometric expansion factor. Pass in a tuple to use different
factors on the two ends of the region.
"""
def __init__(self, *, edge_length_start, edge_length_expansion_factor, **kw):
ones = np.ones(2)
self.edge_length_start = edge_length_start * ones
self.edge_length_expansion_factor = edge_length_expansion_factor * ones
super().__init__(**kw)
[docs]
def local_edge_length(self, x):
start = self.edge_length_start
factor = self.edge_length_expansion_factor
# see doc/mesh.lyx
# mesh_density = x * (factor - 1) + start
x0 = x - self.x0
x1 = self.x1 - x
return np.where(
(x0 >= 0) & (x1 >= 0),
np.minimum(
x0 * (factor[0] - 1) + start[0],
x1 * (factor[1] - 1) + start[1],
),
np.inf,
)
[docs]
class BaseInterval1DTag(object):
''' Class that turns a bunch of arbitrary overlapping intervals
into a mesh. '''
first_cell_value = 1
def __init__(self, intervals):
self.intervals = intervals
@cached_property
def subdomains(self):
return self.intervals_to_subdomains(intervals=self.intervals)
@cached_property
def coordinates(self):
sub = self.subdomains
return self.make_coordinates(
subdomain_to_intervals=sub['subdomain_to_intervals'],
endpoints=sub['endpoints'])
@cached_property
def tag_to_cell_values(self):
''' Mapping from a tag to a set of cell values (e.g. values
inside `self.product2d_mesh.cell_function`). '''
return self.subdomains['tag_to_cell_values']
[docs]
def intervals_to_subdomains(self, intervals):
all_tags = set()
all_tags_update = all_tags.update
endpoints = set()
endpoints_add = endpoints.add
for interval in intervals:
endpoints_add(interval.x0)
endpoints_add(interval.x1)
all_tags_update(interval.tags)
del all_tags_update, endpoints_add
endpoints = list(endpoints)
endpoints.sort()
all_tags = list(all_tags)
all_tags.sort()
endpoint_to_index = {x: i for i, x in enumerate(endpoints)}
# subdomains form a partition of the mesh space
N = (len(endpoints)-1) # number of subdomains
subdomain_to_tags = [set() for i in range(N)]
subdomain_to_intervals = [set() for i in range(N)]
for interval in intervals:
i0 = endpoint_to_index[interval.x0]
i1 = endpoint_to_index[interval.x1]
for i in range(i0, i1):
subdomain_to_intervals[i].add(interval)
subdomain_to_tags[i].update(interval.tags)
# freeze tags into tuples so they're hashable
for i, tags in enumerate(subdomain_to_tags):
subdomain_to_tags[i] = tuple(sorted(tags))
cell_values_start = self.first_cell_value
tagset_to_cell_value = {
ts: cv for cv, ts in enumerate(
sorted(set(subdomain_to_tags)), cell_values_start)}
cell_values_end = cell_values_start + len(tagset_to_cell_value)
subdomain_to_cell_value = [
tagset_to_cell_value[ts] for ts in subdomain_to_tags]
tag_to_cell_values = {tag: set() for tag in all_tags}
for tagset, cell_value in tagset_to_cell_value.items():
for tag in tagset:
tag_to_cell_values[tag].add(cell_value)
# freeze cell value sets
for k, v in tag_to_cell_values.items():
tag_to_cell_values[k] = frozenset(v)
return dict(tag_to_cell_values=tag_to_cell_values,
subdomain_to_cell_value=subdomain_to_cell_value,
subdomain_to_intervals=subdomain_to_intervals,
used_cell_values=range(cell_values_start,
cell_values_end),
endpoints=endpoints)
[docs]
def make_coordinates(self, subdomain_to_intervals, endpoints):
def local_edge_length_function(intervals, x):
return min(interval.local_edge_length(x)
for interval in intervals)
coordinates = []
subdomain_to_coordinate_range = []
x1 = endpoints[0]
last_coordinate_index = 0
for i, intervals in enumerate(subdomain_to_intervals):
x0 = x1
x1 = endpoints[i+1]
lcf = partial(local_edge_length_function,
tuple(iv for iv in intervals
if hasattr(iv, 'local_edge_length')))
coords = self.make_interval_coordinates(x0, x1, lcf)
coordinates.extend(coords)
prev_last_coordinate_index = last_coordinate_index
last_coordinate_index = len(coordinates)
subdomain_to_coordinate_range.append(
range(prev_last_coordinate_index,
last_coordinate_index))
coordinates.append(x1)
return dict(
coordinates=coordinates,
subdomain_to_coordinate_range=subdomain_to_coordinate_range)
[docs]
def make_interval_coordinates(
self, x0, x1, local_edge_length_function):
'''Note: this excludes second endpoint'''
coords = []
x = x0
while True:
coords.append(x)
delta = local_edge_length_function(x)
x += delta
if x >= x1:
break
return coords
[docs]
class Product2DMeshMixin(object):
product2d_Ys = (0.0, 1.0)
Product2DMesh = Product2DMesh
@cached_property
def product2d_mesh(self):
''' Use this to get a readily-constructed Product2D
object. Note that an attribute `cell_function` has been added
to it. '''
s = self.subdomains
c = self.coordinates
return self.make_product2d_mesh(
coordinates=c['coordinates'],
subdomain_to_coordinate_range=c['subdomain_to_coordinate_range'],
subdomain_to_cell_value=s['subdomain_to_cell_value'],
Ys=self.product2d_Ys)
[docs]
def make_product2d_mesh(self, coordinates,
subdomain_to_coordinate_range,
subdomain_to_cell_value, Ys):
pm = self.Product2DMesh(coordinates, Ys)
mf = pm.cell_function = dolfin.MeshFunction("size_t", pm.mesh, 2)
mfw = mf.array()
for crange, cell_value in zip(subdomain_to_coordinate_range,
subdomain_to_cell_value):
for ix in crange:
mfw[pm.cells_at_ix(ix)] = cell_value
return pm
[docs]
class Interval1DMesh(object):
'''A true-1D (interval) dolfin mesh built from sorted x coordinates,
with a cell function attached. Counterpart of :py:class:`Product2DMesh`
for the true-1D route; cell ``ix`` spans ``Xs[ix]`` to ``Xs[ix+1]``.
Created by Claude Fable 5.1 (Anthropic), 2026-09-04.
'''
def __init__(self, Xs):
self.Xs = np.asarray(Xs, dtype='double')
@cached_property
def mesh(self):
return make_1d_mesh_from_points(self.Xs)
@cached_property
def nX(self):
return len(self.Xs)
[docs]
def cells_at_ix(self, ix):
return range(ix, ix + 1)
[docs]
class Interval1DMeshMixin(object):
'''Build a true-1D interval mesh from the tagged intervals, tagging
each cell with the cell value of the subdomain it lies in (same
convention as :py:class:`Product2DMeshMixin`).'''
Interval1DMesh = Interval1DMesh
@cached_property
def interval_1d_mesh(self):
''' Use this to get a readily-constructed :py:class:`Interval1DMesh`
object. Note that an attribute `cell_function` has been added
to it. '''
s = self.subdomains
c = self.coordinates
return self.make_interval_1d_mesh(
coordinates=c['coordinates'],
subdomain_to_coordinate_range=c['subdomain_to_coordinate_range'],
subdomain_to_cell_value=s['subdomain_to_cell_value'])
[docs]
def make_interval_1d_mesh(self, coordinates,
subdomain_to_coordinate_range,
subdomain_to_cell_value):
im = self.Interval1DMesh(coordinates)
mf = im.cell_function = dolfin.MeshFunction("size_t", im.mesh, 1)
mfw = mf.array()
for crange, cell_value in zip(subdomain_to_coordinate_range,
subdomain_to_cell_value):
for ix in crange:
mfw[im.cells_at_ix(ix)] = cell_value
return im
[docs]
class MinimumCoordinateDistanceMixin(object):
minimum_coordinate_distance = 1e-10
[docs]
def make_interval_coordinates(self, x0, x1, *args, **kwargs):
coords = super().make_interval_coordinates(x0, x1, *args, **kwargs)
minimum_coordinate_distance = self.minimum_coordinate_distance
coords = np.array(coords, dtype='object')
keep = np.zeros(len(coords), dtype='bool')
keep[0] = True
min_x = x0
max_x = x1 - minimum_coordinate_distance
for i, x in enumerate(coords):
if x >= min_x:
if x > max_x:
break
keep[i] = True
min_x = x + minimum_coordinate_distance
return list(coords[keep])
[docs]
class Interval1DTag(Product2DMeshMixin, Interval1DMeshMixin,
MinimumCoordinateDistanceMixin,
BaseInterval1DTag):
pass