# -*- coding: utf-8 -*-
# ___________________________________________________________________________
#
# Pyomo: Python Optimization Modeling Objects
# Copyright (c) 2008-2024
# National Technology and Engineering Solutions of Sandia, LLC
# Under the terms of Contract DE-NA0003525 with National Technology and
# Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
# rights in this software.
# This software is distributed under the 3-clause BSD License.
# ___________________________________________________________________________
"""Transformation to deactivate trivial constraints."""
import logging
from pyomo.common.collections import ComponentSet
from pyomo.common.config import (
ConfigBlock,
ConfigValue,
NonNegativeFloat,
document_kwargs_from_configdict,
)
from pyomo.common.errors import InfeasibleConstraintException
from pyomo.core.base.constraint import Constraint
from pyomo.core.base.transformation import TransformationFactory
from pyomo.core.expr.numvalue import value
from pyomo.core.plugins.transform.hierarchy import IsomorphicTransformation
from pyomo.repn import generate_standard_repn
logger = logging.getLogger('pyomo.contrib.preprocessing')
[docs]@TransformationFactory.register(
'contrib.deactivate_trivial_constraints', doc="Deactivate trivial constraints."
)
@document_kwargs_from_configdict('CONFIG')
class TrivialConstraintDeactivator(IsomorphicTransformation):
"""Deactivates trivial constraints.
Trivial constraints take form :math:`k_1 = k_2` or :math:`k_1 \\leq k_2`,
where :math:`k_1` and :math:`k_2` are constants. These constraints
typically arise when variables are fixed.
Keyword arguments below are specified for the ``apply_to`` and
``create_using`` functions.
"""
CONFIG = ConfigBlock("TrivialConstraintDeactivator")
CONFIG.declare(
"tmp",
ConfigValue(
default=False,
domain=bool,
description="True to store a set of transformed constraints for future"
" reversion of the transformation.",
),
)
CONFIG.declare(
"ignore_infeasible",
ConfigValue(
default=False,
domain=bool,
description="True to skip over trivial constraints that are "
"infeasible instead of raising an InfeasibleConstraintException.",
),
)
CONFIG.declare(
"return_trivial",
ConfigValue(
default=[],
description="a list to which the deactivated trivial"
"constraints are appended (side effect)",
),
)
CONFIG.declare(
"tolerance",
ConfigValue(
default=1e-13,
domain=NonNegativeFloat,
description="tolerance on constraint violations",
),
)
def _apply_to(self, instance, **kwargs):
config = self.CONFIG(kwargs)
if config.tmp and not hasattr(instance, '_tmp_trivial_deactivated_constrs'):
instance._tmp_trivial_deactivated_constrs = ComponentSet()
elif config.tmp:
logger.warning(
'Deactivating trivial constraints on the block {} for which '
'trivial constraints were previously deactivated. '
'Reversion will affect all deactivated constraints.'.format(
instance.name
)
)
# Trivial constraints are those that do not contain any variables, ie.
# the polynomial degree is 0
for constr in instance.component_data_objects(
ctype=Constraint, active=True, descend_into=True
):
repn = generate_standard_repn(constr.body)
if not repn.is_constant():
# This constraint is not trivial
continue
# We need to check each constraint to sure that it is not violated.
constr_lb = value(constr.lower) if constr.has_lb() else float('-inf')
constr_ub = value(constr.upper) if constr.has_ub() else float('inf')
constr_value = repn.constant
# Check if the lower bound is violated outside a given tolerance
if constr_value + config.tolerance <= constr_lb:
if config.ignore_infeasible:
continue
else:
raise InfeasibleConstraintException(
'Trivial constraint {} violates LB {} ≤ BODY {}.'.format(
constr.name, constr_lb, constr_value
)
)
# Check if the upper bound is violated outside a given tolerance
if constr_value >= constr_ub + config.tolerance:
if config.ignore_infeasible:
continue
else:
raise InfeasibleConstraintException(
'Trivial constraint {} violates BODY {} ≤ UB {}.'.format(
constr.name, constr_value, constr_ub
)
)
# Constraint is not infeasible. Deactivate it.
if config.tmp:
instance._tmp_trivial_deactivated_constrs.add(constr)
config.return_trivial.append(constr)
constr.deactivate()
[docs] def revert(self, instance):
"""Revert constraints deactivated by the transformation.
Args:
instance: the model instance on which trivial constraints were
earlier deactivated.
"""
for constr in instance._tmp_trivial_deactivated_constrs:
constr.activate()
del instance._tmp_trivial_deactivated_constrs