Source code for cvxpy.expressions.variable
"""
Copyright 2013 Steven Diamond
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""
from __future__ import annotations
from typing import Any, Iterable, Optional, Tuple
import scipy.sparse as sp
import cvxpy.lin_ops.lin_utils as lu
from cvxpy import settings as s
from cvxpy.constraints.constraint import Constraint
from cvxpy.expressions.expression import Expression
from cvxpy.expressions.leaf import Leaf
[docs]
class Variable(Leaf):
"""The optimization variables in a problem."""
def __init__(
self, shape: int | Iterable[int] = (), name: str | None = None,
var_id: int | None = None, **kwargs: Any
):
if var_id is None:
self.id = lu.get_id()
else:
self.id = var_id
if name is None:
self._name = "%s%d" % (s.VAR_PREFIX, self.id)
elif isinstance(name, str):
self._name = name
else:
raise TypeError("Variable name %s must be a string." % name)
self._variable_with_attributes: Variable | None = None
self._value = None
self.delta = None
self.gradient = None
super(Variable, self).__init__(shape, **kwargs)
[docs]
def name(self) -> str:
"""The name of the variable."""
return self._name
def is_constant(self) -> bool:
return False
@property
def grad(self) -> Optional[dict[Variable, sp.csc_matrix]]:
"""Gives the (sub/super)gradient of the expression w.r.t. each variable.
Matrix expressions are vectorized, so the gradient is a matrix.
"""
# TODO(akshayka): Do not assume shape is 2D.
return {self: sp.eye(self.size).tocsc()}
def variables(self) -> list[Variable]:
"""Returns itself as a variable."""
return [self]
def canonicalize(self) -> Tuple[Expression, list[Constraint]]:
"""Returns the graph implementation of the object."""
obj = lu.create_var(self.shape, self.id)
return (obj, [])
def attributes_were_lowered(self) -> bool:
"""True iff variable generated when lowering a variable with attributes."""
return self._variable_with_attributes is not None
def set_variable_of_provenance(self, variable: Variable) -> None:
assert variable.attributes
self._variable_with_attributes = variable
def variable_of_provenance(self) -> Optional[Variable]:
"""Returns a variable with attributes from which this variable was generated."""
return self._variable_with_attributes
def __repr__(self) -> str:
"""String to recreate the variable."""
attr_str = self._get_attr_str()
return f"Variable({self.shape}, {self.__str__()}{attr_str})"