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 Aln├Žs
#
# 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])