Source code for picos.constraints.con_absolute

# coding: utf-8

# ------------------------------------------------------------------------------
# Copyright (C) 2018-2019 Maximilian Stahlberg
#
# This file is part of PICOS.
#
# PICOS is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# PICOS is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
# ------------------------------------------------------------------------------

"""Implementation of :class:`AbsoluteValueConstraint`."""

from collections import namedtuple

from .. import glyphs
from ..apidoc import api_end, api_start
from .constraint import Constraint, ConstraintConversion

_API_START = api_start(globals())
# -------------------------------


[docs]class AbsoluteValueConstraint(Constraint): """Upper bound on an absolute value.""" # TODO: Improve performance: Add two scalar constraints.
[docs] class AffineConversion(ConstraintConversion): """Upper bound on an absolute value to affine inequality conversion."""
[docs] @classmethod def predict(cls, subtype, options): """Implement :meth:`~.constraint.ConstraintConversion.predict`.""" from . import AffineConstraint yield ("con", AffineConstraint.make_type(dim=2, eq=False), 1)
[docs] @classmethod def convert(cls, con, options): """Implement :meth:`~.constraint.ConstraintConversion.convert`.""" from ..modeling import Problem P = Problem() P.add_constraint((con.signedScalar // -con.signedScalar) <= (con.upperBound // con.upperBound)) return P
[docs] @classmethod def dual(cls, auxVarPrimals, auxConDuals, options): """Implement :meth:`~.constraint.ConstraintConversion.dual`.""" assert len(auxConDuals) == 1 if auxConDuals[0] is None: return None else: return auxConDuals[0][1] - auxConDuals[0][0]
[docs] def __init__(self, signedScalar, upperBound): """Construct an :class:`AbsoluteValueConstraint`. :param ~picos.expressions.AffineExpression signedScalar: A scalar expression. :param ~picos.expressions.AffineExpression upperBound: Upper bound on the expression. """ from ..expressions import AffineExpression assert isinstance(signedScalar, AffineExpression) assert isinstance(upperBound, AffineExpression) assert len(signedScalar) == 1 assert len(upperBound) == 1 self.signedScalar = signedScalar self.upperBound = upperBound super(AbsoluteValueConstraint, self).__init__("Absolute Value")
Subtype = namedtuple("Subtype", ()) def _subtype(self): return self.Subtype() @classmethod def _cost(cls, subtype): return 2 def _expression_names(self): yield "signedScalar" yield "upperBound" def _str(self): return glyphs.le( glyphs.abs(self.signedScalar.string), self.upperBound.string) def _get_size(self): return (1, 1) def _get_slack(self): return self.upperBound.value - abs(self.signedScalar.value)
# -------------------------------------- __all__ = api_end(_API_START, globals())