def solver(self, value):
not_valid_interface = SolverNotFound(
"'{}' is not a valid solver interface. Pick one from {}.".format(
value, ", ".join(list(solvers))))
if isinstance(value, string_types):
if value not in solvers:
raise not_valid_interface
interface = solvers[value]
elif isinstance(value, types.ModuleType) and hasattr(value, 'Model'):
interface = value
else:
raise not_valid_interface
self._solver = interface
def solver(self, value) -> None:
"""Set the optlang solver interface."""
not_valid_interface = SolverNotFound(
f"'{value}' is not a valid solver interface. "
f" Please pick one from {', '.join(SOLVERS)}.")
if isinstance(value, str):
if value not in SOLVERS:
raise not_valid_interface
interface = SOLVERS[value]
elif isinstance(value, types.ModuleType) and hasattr(value, "Model"):
interface = value
else:
raise not_valid_interface
self._solver = interface
def solver(self, value):
not_valid_interface = SolverNotFound(
"%s is not a valid solver interface. Pick from %s." %
(value, list(solvers)))
if isinstance(value, six.string_types):
try:
interface = solvers[interface_to_str(value)]
except KeyError:
raise not_valid_interface
elif isinstance(value, types.ModuleType) and hasattr(value, "Model"):
interface = value
elif isinstance(value, optlang.interface.Model):
interface = value.interface
else:
raise not_valid_interface
# Do nothing if the solver did not change
if self.problem == interface:
return
self._solver = interface.Model.clone(self._solver)
def check_solver(obj):
"""Check whether the chosen solver is valid.
Check whether chosen solver is valid and also warn when using
a specialized solver. Will return the optlang interface for the
requested solver.
Parameters
----------
obj : str or optlang.interface or optlang.interface.Model
The chosen solver.
Raises
------
SolverNotFound
If the solver is not valid.
"""
not_valid_interface = SolverNotFound(
f"{obj} is not a valid solver interface. Pick one from {', '.join(solvers)}."
)
if isinstance(obj, str):
try:
interface = solvers[interface_to_str(obj)]
except KeyError:
raise not_valid_interface
elif isinstance(obj, ModuleType) and hasattr(obj, "Model"):
interface = obj
elif isinstance(obj, optlang.interface.Model):
interface = obj.interface
else:
raise not_valid_interface
if interface_to_str(interface) in ["osqp", "coinor_cbc"]:
logger.warning(
"OSQP and CBC are specialized solvers for quadratic programming (QP) and "
"mixed-integer programming (MIP) problems and may not perform well on "
"general LP problems. So unless you intend to solve a QP or MIP problem, "
"we recommend to change the solver back to a general purpose solver "
"like `model.solver = 'glpk'` for instance.")
return interface