def reset_basis(self, basis_type='std'):
'reset initial lp basis'
if basis_type == 'std':
glpk.glp_std_basis(self.lp)
elif basis_type == 'adv':
glpk.glp_adv_basis(self.lp, 0)
else:
assert basis_type == 'cpx'
glpk.glp_cpx_basis(self.lp)
def reset_solver(community):
"""Reset the solver."""
interface = interface_to_str(community.solver.interface)
logger.info("resetting solver, hoping for the best.")
if interface == "cplex":
logger.warning("switching cplex LP algorithm to `network`.")
community.solver.configuration.lp_method = "network"
elif interface == "gurobi":
community.solver.problem.reset()
elif interface == "glpk":
glp_adv_basis(community.solver.problem, 0)
def reset_solver(community):
"""Reset the solver."""
interface = interface_to_str(community.solver.interface)
logger.info("resetting solver, hoping for the best.")
if interface == "cplex":
community.solver.configuration.lp_method = "network"
community.solver.configuration.lp_method = "barrier"
elif interface == "gurobi":
community.solver.problem.reset()
elif interface == "glpk":
glp_adv_basis(community.solver.problem, 0)
elif interface == "osqp":
community.solver.problem.reset()
def _optimize(self):
status = self._run_glp_simplex()
# Sometimes GLPK gets itself stuck with an invalid basis. This will help it get rid of it.
if status == interface.UNDEFINED and self.configuration.presolve is not True:
glp_adv_basis(self.problem, 0)
status = self._run_glp_simplex()
if status == interface.UNDEFINED and self.configuration.presolve is True:
# If presolve is on, status will be undefined if not optimal
self.configuration.presolve = False
status = self._run_glp_simplex()
self.configuration.presolve = True
if self._glpk_is_mip():
status = self._run_glp_mip()
if status == 'undefined' or status == 'infeasible':
# Let's see if the presolver and some scaling can fix this issue
glp_scale_prob(self.problem, GLP_SF_AUTO)
original_presolve_setting = self.configuration.presolve
self.configuration.presolve = True
status = self._run_glp_mip()
self.configuration.presolve = original_presolve_setting
return status
def _optimize(self):
status = self._run_glp_simplex()
# Sometimes GLPK gets itself stuck with an invalid basis. This will help it get rid of it.
if status == interface.UNDEFINED and self.configuration.presolve is not True:
glp_adv_basis(self.problem, 0)
status = self._run_glp_simplex()
if status == interface.UNDEFINED and self.configuration.presolve is True:
# If presolve is on, status will be undefined if not optimal
self.configuration.presolve = False
status = self._run_glp_simplex()
self.configuration.presolve = True
if (glp_get_num_int(self.problem) + glp_get_num_bin(self.problem)) > 0:
status = self._run_glp_mip()
if status == 'undefined' or status == 'infeasible':
# Let's see if the presolver and some scaling can fix this issue
glp_scale_prob(self.problem, GLP_SF_AUTO)
original_presolve_setting = self.configuration.presolve
self.configuration.presolve = True
status = self._run_glp_mip()
self.configuration.presolve = original_presolve_setting
return status