def _apply_to(self, model, detect_fixed_vars=True):
"""Apply the transformation to the given model."""
# Generate the equality sets
eq_var_map = _build_equality_set(model)
# Detect and process fixed variables.
if detect_fixed_vars:
_fix_equality_fixed_variables(model)
# Generate aggregation infrastructure
model._var_aggregator_info = Block(
doc="Holds information for the variable aggregation "
"transformation system.")
z = model._var_aggregator_info.z = VarList(doc="Aggregated variables.")
# Map of the aggregate var to the equalty set (ComponentSet)
z_to_vars = model._var_aggregator_info.z_to_vars = ComponentMap()
# Map of variables to their corresponding aggregate var
var_to_z = model._var_aggregator_info.var_to_z = ComponentMap()
processed_vars = ComponentSet()
# TODO This iteritems is sorted by the variable name of the key in
# order to preserve determinism. Unfortunately, var.name() is an
# expensive operation right now.
for var, eq_set in sorted(eq_var_map.items(),
key=lambda tup: tup[0].name):
if var in processed_vars:
continue # Skip already-process variables
# This would be weird. The variable hasn't been processed, but is
# in the map. Raise an exception.
assert var_to_z.get(var, None) is None
z_agg = z.add()
z_to_vars[z_agg] = eq_set
var_to_z.update(ComponentMap((v, z_agg) for v in eq_set))
# Set the bounds of the aggregate variable based on the bounds of
# the variables in its equality set.
z_agg.setlb(max_if_not_None(v.lb for v in eq_set if v.has_lb()))
z_agg.setub(min_if_not_None(v.ub for v in eq_set if v.has_ub()))
# Set the fixed status of the aggregate var
fixed_vars = [v for v in eq_set if v.fixed]
if fixed_vars:
# Check to make sure all the fixed values are the same.
if any(var.value != fixed_vars[0].value
for var in fixed_vars[1:]):
raise ValueError(
"Aggregate variable for equality set is fixed to "
"multiple different values: %s" % (fixed_vars, ))
z_agg.fix(fixed_vars[0].value)
# Check that the fixed value lies within bounds.
if z_agg.has_lb() and z_agg.value < value(z_agg.lb):
raise ValueError(
"Aggregate variable for equality set is fixed to "
"a value less than its lower bound: %s < LB %s" %
(z_agg.value, value(z_agg.lb)))
if z_agg.has_ub() and z_agg.value > value(z_agg.ub):
raise ValueError(
"Aggregate variable for equality set is fixed to "
"a value greater than its upper bound: %s > UB %s" %
(z_agg.value, value(z_agg.ub)))
else:
# Set the value to be the average of the values within the
# bounds only if the value is not already fixed.
values_within_bounds = [
v.value for v in eq_set if (v.value is not None and (
not z_agg.has_lb() or v.value >= value(z_agg.lb)) and (
not z_agg.has_ub() or v.value <= value(z_agg.ub)))
]
if values_within_bounds:
z_agg.set_value(sum(values_within_bounds) /
len(values_within_bounds),
skip_validation=True)
processed_vars.update(eq_set)
# Do the substitution
substitution_map = {id(var): z_var for var, z_var in var_to_z.items()}
visitor = ExpressionReplacementVisitor(
substitute=substitution_map,
descend_into_named_expressions=True,
remove_named_expressions=False,
)
for constr in model.component_data_objects(ctype=Constraint,
active=True):
orig_body = constr.body
new_body = visitor.walk_expression(constr.body)
if orig_body is not new_body:
constr.set_value((constr.lower, new_body, constr.upper))
for objective in model.component_data_objects(ctype=Objective,
active=True):
orig_expr = objective.expr
new_expr = visitor.walk_expression(objective.expr)
if orig_expr is not new_expr:
objective.set_value(new_expr)
def _replace_parameters_in_constraints(self, variableSubMap):
instance = self.model_instance
block = self.block
# Visitor that we will use to replace user-provided parameters
# in the objective and the constraints.
param_replacer = ExpressionReplacementVisitor(
substitute=variableSubMap,
remove_named_expressions=True,
)
# TODO: Flag to ExpressionReplacementVisitor to only replace
# named expressions if a node has been replaced within that
# expression.
new_old_comp_map = ComponentMap()
# clone Objective, add to Block, and update any Expressions
for obj in list(
instance.component_data_objects(Objective,
active=True,
descend_into=True)):
tempName = unique_component_name(block, obj.local_name)
new_expr = param_replacer.walk_expression(obj.expr)
block.add_component(tempName, Objective(expr=new_expr))
new_old_comp_map[block.component(tempName)] = obj
obj.deactivate()
# clone Constraints, add to Block, and update any Expressions
#
# Unfortunate that this deactivates and replaces constraints
# even if they don't contain the parameters.
#
old_con_list = list(
instance.component_data_objects(Constraint,
active=True,
descend_into=True))
last_idx = 0
for con in old_con_list:
if (con.equality or con.lower is None or con.upper is None):
new_expr = param_replacer.walk_expression(con.expr)
block.constList.add(expr=new_expr)
last_idx += 1
new_old_comp_map[block.constList[last_idx]] = con
else:
# Constraint must be a ranged inequality, break into
# separate constraints
new_body = param_replacer.walk_expression(con.body)
new_lower = param_replacer.walk_expression(con.lower)
new_upper = param_replacer.walk_expression(con.upper)
# Add constraint for lower bound
block.constList.add(expr=(new_lower <= new_body))
last_idx += 1
new_old_comp_map[block.constList[last_idx]] = con
# Add constraint for upper bound
block.constList.add(expr=(new_body <= new_upper))
last_idx += 1
new_old_comp_map[block.constList[last_idx]] = con
con.deactivate()
return new_old_comp_map