def init_custom_disjuncts(solve_data, config):
"""Initialize by using user-specified custom disjuncts."""
# TODO error checking to make sure that the user gave proper disjuncts
for active_disjunct_set in config.custom_init_disjuncts:
# custom_init_disjuncts contains a list of sets, giving the disjuncts
# active at each initialization iteration
# fix the disjuncts in the linear GDP and send for solution.
solve_data.mip_iteration += 1
linear_GDP = solve_data.linear_GDP.clone()
config.logger.info(
"Generating initial linear GDP approximation by "
"solving subproblems with user-specified active disjuncts.")
for orig_disj, clone_disj in zip(
solve_data.original_model.GDPopt_utils.disjunct_list,
linear_GDP.GDPopt_utils.disjunct_list):
if orig_disj in active_disjunct_set:
clone_disj.indicator_var.fix(True)
mip_result = solve_linear_GDP(linear_GDP, solve_data, config)
if mip_result.feasible:
nlp_result = solve_disjunctive_subproblem(mip_result, solve_data,
config)
if nlp_result.feasible:
add_subproblem_cuts(nlp_result, solve_data, config)
add_integer_cut(mip_result.var_values,
solve_data.linear_GDP,
solve_data,
config,
feasible=nlp_result.feasible)
else:
config.logger.error('Linear GDP infeasible for user-specified '
'custom initialization disjunct set %s. '
'Skipping that set and continuing on.' %
list(disj.name
for disj in active_disjunct_set))
def init_fixed_disjuncts(solve_data, config):
"""Initialize by solving the problem with the current disjunct values."""
# TODO error checking to make sure that the user gave proper disjuncts
# fix the disjuncts in the linear GDP and send for solution.
solve_data.mip_iteration += 1
config.logger.info(
"Generating initial linear GDP approximation by "
"solving subproblem with original user-specified disjunct values.")
linear_GDP = solve_data.linear_GDP.clone()
TransformationFactory('gdp.fix_disjuncts').apply_to(linear_GDP)
mip_result = solve_linear_GDP(linear_GDP, solve_data, config)
if mip_result.feasible:
nlp_result = solve_disjunctive_subproblem(mip_result, solve_data,
config)
if nlp_result.feasible:
add_subproblem_cuts(nlp_result, solve_data, config)
add_integer_cut(mip_result.var_values,
solve_data.linear_GDP,
solve_data,
config,
feasible=nlp_result.feasible)
else:
config.logger.error('Linear GDP infeasible for initial user-specified '
'disjunct values. '
'Skipping initialization.')
def init_custom_disjuncts(solve_data, config):
"""Initialize by using user-specified custom disjuncts."""
# TODO error checking to make sure that the user gave proper disjuncts
for active_disjunct_set in config.custom_init_disjuncts:
# custom_init_disjuncts contains a list of sets, giving the disjuncts
# active at each initialization iteration
# fix the disjuncts in the linear GDP and send for solution.
solve_data.mip_iteration += 1
linear_GDP = solve_data.linear_GDP.clone()
config.logger.info(
"Generating initial linear GDP approximation by "
"solving subproblems with user-specified active disjuncts.")
for orig_disj, clone_disj in zip(
solve_data.original_model.GDPopt_utils.disjunct_list,
linear_GDP.GDPopt_utils.disjunct_list
):
if orig_disj in active_disjunct_set:
clone_disj.indicator_var.fix(1)
mip_result = solve_linear_GDP(linear_GDP, solve_data, config)
if mip_result.feasible:
nlp_result = solve_disjunctive_subproblem(mip_result, solve_data, config)
if nlp_result.feasible:
add_subproblem_cuts(nlp_result, solve_data, config)
add_integer_cut(
mip_result.var_values, solve_data.linear_GDP, solve_data,
config, feasible=nlp_result.feasible)
else:
config.logger.error(
'Linear GDP infeasible for user-specified '
'custom initialization disjunct set %s. '
'Skipping that set and continuing on.'
% list(disj.name for disj in active_disjunct_set))
def init_max_binaries(solve_data, config):
"""Initialize by maximizing binary variables and disjuncts.
This function activates as many binary variables and disjucts as
feasible.
"""
solve_data.mip_iteration += 1
linear_GDP = solve_data.linear_GDP.clone()
config.logger.info(
"Generating initial linear GDP approximation by "
"solving a subproblem that maximizes "
"the sum of all binary and logical variables.")
# Set up binary maximization objective
next(linear_GDP.component_data_objects(Objective, active=True)).deactivate()
binary_vars = (
v for v in linear_GDP.component_data_objects(
ctype=Var, descend_into=(Block, Disjunct))
if v.is_binary() and not v.fixed)
linear_GDP.GDPopt_utils.max_binary_obj = Objective(
expr=sum(binary_vars), sense=maximize)
# Solve
mip_results = solve_linear_GDP(linear_GDP, solve_data, config)
if mip_results.feasible:
nlp_result = solve_disjunctive_subproblem(mip_results, solve_data, config)
if nlp_result.feasible:
add_subproblem_cuts(nlp_result, solve_data, config)
add_integer_cut(mip_results.var_values, solve_data.linear_GDP, solve_data, config,
feasible=nlp_result.feasible)
else:
config.logger.info(
"Linear relaxation for initialization was infeasible. "
"Problem is infeasible.")
return False
def init_fixed_disjuncts(solve_data, config):
"""Initialize by solving the problem with the current disjunct values."""
# TODO error checking to make sure that the user gave proper disjuncts
# fix the disjuncts in the linear GDP and send for solution.
solve_data.mip_iteration += 1
config.logger.info(
"Generating initial linear GDP approximation by "
"solving subproblem with original user-specified disjunct values.")
linear_GDP = solve_data.linear_GDP.clone()
TransformationFactory('gdp.fix_disjuncts').apply_to(linear_GDP)
mip_result = solve_linear_GDP(linear_GDP, solve_data, config)
if mip_result.feasible:
nlp_result = solve_disjunctive_subproblem(mip_result, solve_data, config)
if nlp_result.feasible:
add_subproblem_cuts(nlp_result, solve_data, config)
add_integer_cut(
mip_result.var_values, solve_data.linear_GDP, solve_data, config,
feasible=nlp_result.feasible)
else:
config.logger.error(
'Linear GDP infeasible for initial user-specified '
'disjunct values. '
'Skipping initialization.')
def init_set_covering(solve_data, config):
"""Initialize by solving problems to cover the set of all disjuncts.
The purpose of this initialization is to generate linearizations
corresponding to each of the disjuncts.
This work is based upon prototyping work done by Eloy Fernandez at
Carnegie Mellon University.
"""
config.logger.info("Starting set covering initialization.")
# List of True/False if the corresponding disjunct in
# disjunct_list still needs to be covered by the initialization
disjunct_needs_cover = list(
any(constr.body.polynomial_degree() not in (0, 1)
for constr in disj.component_data_objects(
ctype=Constraint, active=True, descend_into=True))
for disj in solve_data.working_model.GDPopt_utils.disjunct_list)
# Set up set covering mip
set_cover_mip = solve_data.linear_GDP.clone()
# Deactivate nonlinear constraints
for obj in set_cover_mip.component_data_objects(Objective, active=True):
obj.deactivate()
iter_count = 1
while (any(disjunct_needs_cover)
and iter_count <= config.set_cover_iterlim):
config.logger.info("%s disjuncts need to be covered." %
disjunct_needs_cover.count(True))
# Solve set covering MIP
mip_result = solve_set_cover_mip(set_cover_mip, disjunct_needs_cover,
solve_data, config)
if not mip_result.feasible:
# problem is infeasible. break
return False
# solve local NLP
subprob_result = solve_disjunctive_subproblem(mip_result, solve_data,
config)
if subprob_result.feasible:
# if successful, updated sets
active_disjuncts = list(
fabs(val - 1) <= config.integer_tolerance
for val in mip_result.disjunct_values)
# Update the disjunct needs cover list
disjunct_needs_cover = list((needed_cover and not was_active) for (
needed_cover,
was_active) in zip(disjunct_needs_cover, active_disjuncts))
add_subproblem_cuts(subprob_result, solve_data, config)
add_integer_cut(mip_result.var_values,
solve_data.linear_GDP,
solve_data,
config,
feasible=subprob_result.feasible)
add_integer_cut(mip_result.var_values,
set_cover_mip,
solve_data,
config,
feasible=subprob_result.feasible)
iter_count += 1
if any(disjunct_needs_cover):
# Iteration limit was hit without a full covering of all nonlinear
# disjuncts
config.logger.warning(
'Iteration limit reached for set covering initialization '
'without covering all disjuncts.')
return False
config.logger.info("Initialization complete.")
return True
def init_set_covering(solve_data, config):
"""Initialize by solving problems to cover the set of all disjuncts.
The purpose of this initialization is to generate linearizations
corresponding to each of the disjuncts.
This work is based upon prototyping work done by Eloy Fernandez at
Carnegie Mellon University.
"""
config.logger.info("Starting set covering initialization.")
# List of True/False if the corresponding disjunct in
# disjunct_list still needs to be covered by the initialization
disjunct_needs_cover = list(
any(constr.body.polynomial_degree() not in (0, 1)
for constr in disj.component_data_objects(
ctype=Constraint, active=True, descend_into=True))
for disj in solve_data.working_model.GDPopt_utils.disjunct_list)
# Set up set covering mip
set_cover_mip = solve_data.linear_GDP.clone()
# Deactivate nonlinear constraints
for obj in set_cover_mip.component_data_objects(Objective, active=True):
obj.deactivate()
iter_count = 1
while (any(disjunct_needs_cover) and
iter_count <= config.set_cover_iterlim):
config.logger.info(
"%s disjuncts need to be covered." %
disjunct_needs_cover.count(True)
)
# Solve set covering MIP
mip_result = solve_set_cover_mip(
set_cover_mip, disjunct_needs_cover, solve_data, config)
if not mip_result.feasible:
# problem is infeasible. break
return False
# solve local NLP
subprob_result = solve_disjunctive_subproblem(mip_result, solve_data, config)
if subprob_result.feasible:
# if successful, updated sets
active_disjuncts = list(
fabs(val - 1) <= config.integer_tolerance
for val in mip_result.disjunct_values)
# Update the disjunct needs cover list
disjunct_needs_cover = list(
(needed_cover and not was_active)
for (needed_cover, was_active) in zip(disjunct_needs_cover,
active_disjuncts))
add_subproblem_cuts(subprob_result, solve_data, config)
add_integer_cut(
mip_result.var_values, solve_data.linear_GDP, solve_data, config,
feasible=subprob_result.feasible)
add_integer_cut(
mip_result.var_values, set_cover_mip, solve_data, config,
feasible=subprob_result.feasible)
iter_count += 1
if any(disjunct_needs_cover):
# Iteration limit was hit without a full covering of all nonlinear
# disjuncts
config.logger.warning(
'Iteration limit reached for set covering initialization '
'without covering all disjuncts.')
return False
config.logger.info("Initialization complete.")
return True