# ____________________________________________________________________________________
#
# Pyomo: Python Optimization Modeling Objects
# Copyright (c) 2008-2026 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.
# ____________________________________________________________________________________
from pyomo.contrib.piecewise.piecewise_linear_expression import (
PiecewiseLinearExpression,
)
from pyomo.core import Expression
from pyomo.core.expr.visitor import StreamBasedExpressionVisitor
[docs]
class PiecewiseLinearToMIP(StreamBasedExpressionVisitor):
"""
Expression walker to replace PiecewiseLinearExpressions when creating
equivalent MIP formulations.
Args:
transform_pw_linear_expression (function): a callback that accepts
a PiecewiseLinearExpression, its parent PiecewiseLinearFunction,
and a transformation Block. It is expected to convert the
PiecewiseLinearExpression to MIP form, and return the Var (or
other expression) that will replace it in the expression.
transBlock (Block): transformation Block to pass to the above
callback
"""
[docs]
def __init__(self, transform_pw_linear_expression, transBlock):
self.transform_pw_linear_expression = transform_pw_linear_expression
self.transBlock = transBlock
self._process_node = self._process_node_bx
def initializeWalker(self, expr):
expr, src, src_idx = expr
# always walk
return True, expr
def beforeChild(self, node, child, child_idx):
return True, None
def exitNode(self, node, data):
if node.__class__ is PiecewiseLinearExpression:
parent = node.pw_linear_function
substitute_var = self.transform_pw_linear_expression(
node, parent, self.transBlock
)
parent._expressions[parent._expression_ids[node]] = substitute_var
return node
finalizeResult = None