Source code for pyomo.contrib.preprocessing.plugins.deactivate_trivial_constraints

# -*- coding: utf-8 -*-

#  ___________________________________________________________________________
#
#  Pyomo: Python Optimization Modeling Objects
#  Copyright 2017 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,
                                 add_docstring_list)
from pyomo.core.base.constraint import Constraint
from pyomo.core.base.plugin import TransformationFactory
from pyomo.core.expr.numvalue import value
from pyomo.core.plugins.transform.hierarchy import IsomorphicTransformation

logger = logging.getLogger('pyomo.contrib.preprocessing')

[docs]@TransformationFactory.register( 'contrib.deactivate_trivial_constraints', doc="Deactivate trivial constraints.") 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 a ValueError." )) 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" )) __doc__ = add_docstring_list(__doc__, CONFIG) 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 trivial_constraints = ( constr for constr in instance.component_data_objects( ctype=Constraint, active=True, descend_into=True) if constr.body.polynomial_degree() == 0) for constr in trivial_constraints: # 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 = value(constr.body) # 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 ValueError( '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 ValueError( '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