def copy(self: Solver, solver_name: str = "") -> "Model":
""" Creates a copy of the current model
Args:
solver_name(str): solver name (optional)
Returns:
clone of current model
"""
if not solver_name:
solver_name = self.solver_name
copy = Model(self.name, self.sense, solver_name)
# adding variables
for v in self.vars:
copy.add_var(name=v.name,
lb=v.lb,
ub=v.ub,
obj=v.obj,
var_type=v.var_type)
# adding constraints
for c in self.constrs:
orig_expr = c.expr
expr = LinExpr(const=orig_expr.const, sense=orig_expr.sense)
for (var, value) in orig_expr.expr.items():
expr.add_term(self.vars[var.idx], value)
copy.add_constr(lin_expr=expr, name=c.name)
# setting objective function"s constant
copy.objective_const = self.objective_const
return copy
def objective(self: "Model", objective):
if isinstance(objective, (int, float)):
self.solver.set_objective(LinExpr([], [], objective))
elif isinstance(objective, Var):
self.solver.set_objective(LinExpr([objective], [1]))
elif isinstance(objective, LinExpr):
self.solver.set_objective(objective)
def objective(self: Solver, objective):
if isinstance(objective, (int, float)):
self.solver.set_objective(LinExpr([], [], objective))
elif isinstance(objective, Var):
self.solver.set_objective(LinExpr([objective], [1]))
elif isinstance(objective, LinExpr):
if objective.sense == MAXIMIZE:
self.solver.set_objective_sense(MAXIMIZE)
elif objective.sense == MINIMIZE:
self.solver.set_objective_sense(MINIMIZE)
self.solver.set_objective(objective)
def xsum(terms) -> LinExpr:
"""
Function that should be used to create a linear expression from a summation.
While the python function sum() can also be used, this function is optimized
version for quickly generating the linear expression.
Args:
terms: set (ideally a list) of terms to be summed
"""
result = LinExpr()
for term in terms:
result.add_term(term)
return result
def minimize(expr: LinExpr) -> LinExpr:
"""
Function that should be used to set the objective function to MINIMIZE
a given linear expression (passed as argument).
Args:
expr(LinExpr): linear expression
"""
expr.sense = MINIMIZE
return expr