Coverage for picos/constraints/con_expcone.py: 92.11%
38 statements
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« prev ^ index » next coverage.py v6.5.0, created at 2023-02-15 14:21 +0000
1# ------------------------------------------------------------------------------
2# Copyright (C) 2018-2019 Maximilian Stahlberg
3#
4# This file is part of PICOS.
5#
6# PICOS is free software: you can redistribute it and/or modify it under the
7# terms of the GNU General Public License as published by the Free Software
8# Foundation, either version 3 of the License, or (at your option) any later
9# version.
10#
11# PICOS is distributed in the hope that it will be useful, but WITHOUT ANY
12# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
13# A PARTICULAR PURPOSE. See the GNU General Public License for more details.
14#
15# You should have received a copy of the GNU General Public License along with
16# this program. If not, see <http://www.gnu.org/licenses/>.
17# ------------------------------------------------------------------------------
19"""Implementation of :class:`ExpConeConstraint`."""
21from collections import namedtuple
23import numpy
25from .. import glyphs
26from ..apidoc import api_end, api_start
27from ..caching import cached_property
28from .constraint import Constraint
30_API_START = api_start(globals())
31# -------------------------------
34class ExpConeConstraint(Constraint):
35 r"""Exponential cone membership constraint.
37 An exponential cone constraint stating that :math:`(x, y, z)` fulfills
38 :math:`x \geq y e^{\frac{z}{y}} \land x > 0 \land y > 0`.
39 """
41 def __init__(self, element, customString=None):
42 """Construct an :class:`ExpConeConstraint`.
44 :param ~picos.expressions.AffineExpression element:
45 Three-dimensional expression representing the vector
46 :math:`(x, y, z)`.
47 :param str customString:
48 Optional string description.
49 """
50 from ..expressions import AffineExpression
52 assert isinstance(element, AffineExpression)
53 assert len(element) == 3
55 self.element = element
57 super(ExpConeConstraint, self).__init__(
58 "Exponential Cone", customString, printSize=False)
60 x = property(lambda self: self.element[0])
61 y = property(lambda self: self.element[1])
62 z = property(lambda self: self.element[2])
64 @cached_property
65 def conic_membership_form(self):
66 """Implement for :class:`~.constraint.ConicConstraint`."""
67 from ..expressions import ExponentialCone
68 return self.element.vec, ExponentialCone()
70 Subtype = namedtuple("Subtype", ())
72 def _subtype(self):
73 return self.Subtype()
75 @classmethod
76 def _cost(cls, subtype):
77 return 3
79 def _expression_names(self):
80 yield "element"
82 def _str(self):
83 return glyphs.ge(self.element[0].string,
84 glyphs.mul(self.element[1].string, glyphs.exp(glyphs.div(
85 self.element[2].string, self.element[1].string))))
87 def _get_size(self):
88 return (3, 1)
90 def _get_slack(self):
91 x = self.element.safe_value
93 # TODO: Also consider x_1 > 0 and x_2 > 0 by projecting x on the cone's
94 # surface and measuring the distance between the projection and x.
95 return x[0] - x[1] * numpy.exp(x[2] / x[1])
98# --------------------------------------
99__all__ = api_end(_API_START, globals())