def handle_lazy_main_feasible_solution_gurobi(cb_m, cb_opt, solve_data,
config):
"""This function is called during the branch and bound of main MIP problem,
more exactly when a feasible solution is found and LazyCallback is activated.
Copy the solution to working model and update upper or lower bound.
In LP-NLP, upper or lower bound are updated during solving the main problem.
Parameters
----------
cb_m : Pyomo model
The MIP main problem.
cb_opt : SolverFactory
The gurobi_persistent solver.
solve_data : MindtPySolveData
Data container that holds solve-instance data.
config : ConfigBlock
The specific configurations for MindtPy.
"""
# proceed. Just need integer values
cb_opt.cbGetSolution(vars=cb_m.MindtPy_utils.variable_list)
# this value copy is useful since we need to fix subproblem based on the solution of the main problem
copy_var_list_values(cb_m.MindtPy_utils.variable_list,
solve_data.working_model.MindtPy_utils.variable_list,
config)
update_dual_bound(solve_data,
cb_opt.cbGet(gurobipy.GRB.Callback.MIPSOL_OBJBND))
config.logger.info(
solve_data.log_formatter.format(
solve_data.mip_iter, 'restrLP',
cb_opt.cbGet(gurobipy.GRB.Callback.MIPSOL_OBJ),
solve_data.primal_bound, solve_data.dual_bound, solve_data.rel_gap,
get_main_elapsed_time(solve_data.timing)))
def handle_lazy_main_feasible_solution(self, main_mip, solve_data, config,
opt):
"""This function is called during the branch and bound of main mip, more
exactly when a feasible solution is found and LazyCallback is activated.
Copy the result to working model and update upper or lower bound.
In LP-NLP, upper or lower bound are updated during solving the main problem.
Parameters
----------
main_mip : Pyomo model
The MIP main problem.
solve_data : MindtPySolveData
Data container that holds solve-instance data.
config : ConfigBlock
The specific configurations for MindtPy.
opt : SolverFactory
The cplex_persistent solver.
"""
# proceed. Just need integer values
# this value copy is useful since we need to fix subproblem based on the solution of the main problem
self.copy_lazy_var_list_values(
opt, main_mip.MindtPy_utils.variable_list,
solve_data.working_model.MindtPy_utils.variable_list, config)
update_dual_bound(solve_data, self.get_best_objective_value())
config.logger.info(
solve_data.log_formatter.format(
solve_data.mip_iter, 'restrLP', self.get_objective_value(),
solve_data.primal_bound, solve_data.dual_bound,
solve_data.rel_gap, get_main_elapsed_time(solve_data.timing)))
def handle_main_optimal(main_mip, solve_data, config, update_bound=True):
"""This function copies the results from 'solve_main' to the working model and updates the upper/lower bound. This
function is called after an optimal solution is found for the main problem.
Args:
main_mip (Pyomo model): the MIP main problem.
solve_data (MindtPySolveData): data container that holds solve-instance data.
config (ConfigBlock): the specific configurations for MindtPy.
update_bound (bool, optional): whether update the bound. Bound will not be updated when handle regularization problem. Defaults to True.
"""
# proceed. Just need integer values
MindtPy = main_mip.MindtPy_utils
# check if the value of binary variable is valid
for var in MindtPy.discrete_variable_list:
if var.value is None:
config.logger.warning(
f"Integer variable {var.name} not initialized. "
"Setting it to its lower bound")
var.set_value(var.lb, skip_validation=True) # nlp_var.bounds[0]
# warm start for the nlp subproblem
copy_var_list_values(main_mip.MindtPy_utils.variable_list,
solve_data.working_model.MindtPy_utils.variable_list,
config)
if update_bound:
update_dual_bound(solve_data, value(MindtPy.mip_obj.expr))
config.logger.info(
solve_data.log_formatter.format(
solve_data.mip_iter, 'MILP', value(MindtPy.mip_obj.expr),
solve_data.LB, solve_data.UB, solve_data.rel_gap,
get_main_elapsed_time(solve_data.timing)))
def init_rNLP(solve_data, config):
"""Initialize the problem by solving the relaxed NLP and then store the optimal variable
values obtained from solving the rNLP.
Parameters
----------
solve_data : MindtPySolveData
Data container that holds solve-instance data.
config : ConfigBlock
The specific configurations for MindtPy.
Raises
------
ValueError
MindtPy unable to handle the termination condition of the relaxed NLP.
"""
m = solve_data.working_model.clone()
config.logger.debug('Relaxed NLP: Solve relaxed integrality')
MindtPy = m.MindtPy_utils
TransformationFactory('core.relax_integer_vars').apply_to(m)
nlp_args = dict(config.nlp_solver_args)
nlpopt = SolverFactory(config.nlp_solver)
set_solver_options(nlpopt, solve_data, config, solver_type='nlp')
with SuppressInfeasibleWarning():
results = nlpopt.solve(m, tee=config.nlp_solver_tee, **nlp_args)
subprob_terminate_cond = results.solver.termination_condition
if subprob_terminate_cond in {tc.optimal, tc.feasible, tc.locallyOptimal}:
main_objective = MindtPy.objective_list[-1]
if subprob_terminate_cond == tc.optimal:
update_dual_bound(solve_data, value(main_objective.expr))
else:
config.logger.info('relaxed NLP is not solved to optimality.')
update_suboptimal_dual_bound(solve_data, results)
dual_values = list(
m.dual[c] for c in
MindtPy.constraint_list) if config.calculate_dual else None
config.logger.info(
solve_data.log_formatter.format(
'-', 'Relaxed NLP', value(main_objective.expr), solve_data.LB,
solve_data.UB, solve_data.rel_gap,
get_main_elapsed_time(solve_data.timing)))
# Add OA cut
if config.strategy in {'OA', 'GOA', 'FP'}:
copy_var_list_values(m.MindtPy_utils.variable_list,
solve_data.mip.MindtPy_utils.variable_list,
config,
ignore_integrality=True)
if config.init_strategy == 'FP':
copy_var_list_values(
m.MindtPy_utils.variable_list,
solve_data.working_model.MindtPy_utils.variable_list,
config,
ignore_integrality=True)
if config.strategy in {'OA', 'FP'}:
add_oa_cuts(solve_data.mip, dual_values, solve_data, config)
elif config.strategy == 'GOA':
add_affine_cuts(solve_data, config)
for var in solve_data.mip.MindtPy_utils.discrete_variable_list:
# We don't want to trigger the reset of the global stale
# indicator, so we will set this variable to be "stale",
# knowing that set_value will switch it back to "not
# stale"
var.stale = True
var.set_value(int(round(var.value)), skip_validation=True)
elif subprob_terminate_cond in {tc.infeasible, tc.noSolution}:
# TODO fail? try something else?
config.logger.info('Initial relaxed NLP problem is infeasible. '
'Problem may be infeasible.')
elif subprob_terminate_cond is tc.maxTimeLimit:
config.logger.info(
'NLP subproblem failed to converge within time limit.')
solve_data.results.solver.termination_condition = tc.maxTimeLimit
elif subprob_terminate_cond is tc.maxIterations:
config.logger.info(
'NLP subproblem failed to converge within iteration limit.')
else:
raise ValueError(
'MindtPy unable to handle relaxed NLP termination condition '
'of %s. Solver message: %s' %
(subprob_terminate_cond, results.solver.message))
