Source code for ufl.variable
# -*- coding: utf-8 -*-
"""Defines the Variable and Label classes, used to label
expressions as variables for differentiation."""
# Copyright (C) 2008-2016 Martin Sandve Alnæs
#
# This file is part of UFL (https://www.fenicsproject.org)
#
# SPDX-License-Identifier: LGPL-3.0-or-later
from ufl.utils.counted import counted_init
from ufl.log import error
from ufl.core.expr import Expr
from ufl.core.ufl_type import ufl_type
from ufl.core.terminal import Terminal
from ufl.core.operator import Operator
from ufl.constantvalue import as_ufl
[docs]@ufl_type()
class Label(Terminal):
__slots__ = ("_count",)
_globalcount = 0
def __init__(self, count=None):
Terminal.__init__(self)
counted_init(self, count, Label)
[docs] def count(self):
return self._count
def __str__(self):
return "Label(%d)" % self._count
def __repr__(self):
r = "Label(%d)" % self._count
return r
@property
def ufl_shape(self):
error("Label has no shape (it is not a tensor expression).")
@property
def ufl_free_indices(self):
error("Label has no free indices (it is not a tensor expression).")
@property
def ufl_index_dimensions(self):
error("Label has no free indices (it is not a tensor expression).")
[docs] def is_cellwise_constant(self):
return True
[docs] def ufl_domains(self):
"Return tuple of domains related to this terminal object."
return ()
[docs]@ufl_type(is_shaping=True, is_index_free=True, num_ops=1, inherit_shape_from_operand=0)
class Variable(Operator):
"""A Variable is a representative for another expression.
It will be used by the end-user mainly for defining
a quantity to differentiate w.r.t. using diff.
Example::
e = <...>
e = variable(e)
f = exp(e**2)
df = diff(f, e)
"""
__slots__ = ()
def __init__(self, expression, label=None):
# Conversion
expression = as_ufl(expression)
if label is None:
label = Label()
# Checks
if not isinstance(expression, Expr):
error("Expecting Expr.")
if not isinstance(label, Label):
error("Expecting a Label.")
if expression.ufl_free_indices:
error("Variable cannot wrap an expression with free indices.")
Operator.__init__(self, (expression, label))
[docs] def ufl_domains(self):
return self.ufl_operands[0].ufl_domains()
[docs] def evaluate(self, x, mapping, component, index_values):
a = self.ufl_operands[0].evaluate(x, mapping, component, index_values)
return a
[docs] def expression(self):
return self.ufl_operands[0]
[docs] def label(self):
return self.ufl_operands[1]
def __eq__(self, other):
return (isinstance(other, Variable) and
self.ufl_operands[1] == other.ufl_operands[1] and
self.ufl_operands[0] == other.ufl_operands[0])
def __str__(self):
return "var%d(%s)" % (self.ufl_operands[1].count(),
self.ufl_operands[0])