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removing constraints from gurobi
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@Dimosts
Dimosts committed Sep 7, 2023
1 parent 008f269 commit 7a7d06f
Showing 1 changed file with 29 additions and 15 deletions.
44 changes: 29 additions & 15 deletions cpmpy/solvers/gurobi.py
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,7 @@ def __init__(self, cpm_model=None, subsolver=None):

# TODO: subsolver could be a GRB_ENV if a user would want to hand one over
self.grb_model = gp.Model(env=GRB_ENV)
self.cons = []

# initialise everything else and post the constraints/objective
# it is sufficient to implement __add__() and minimize/maximize() below
Expand Down Expand Up @@ -313,27 +314,28 @@ def __add__(self, cpm_expr_orig):
# Thanks to `only_numexpr_equality()` only supported comparisons should remain
if cpm_expr.name == '<=':
grblhs = self._make_numexpr(lhs)
self.grb_model.addLConstr(grblhs, GRB.LESS_EQUAL, grbrhs)
self.cons.append([self.grb_model.addLConstr(grblhs, GRB.LESS_EQUAL, grbrhs), cpm_expr_orig])

elif cpm_expr.name == '>=':
grblhs = self._make_numexpr(lhs)
self.grb_model.addLConstr(grblhs, GRB.GREATER_EQUAL, grbrhs)
self.cons.append([self.grb_model.addLConstr(grblhs, GRB.GREATER_EQUAL, grbrhs), cpm_expr_orig])
elif cpm_expr.name == '==':
if isinstance(lhs, _NumVarImpl) \
or (isinstance(lhs, Operator) and (lhs.name == 'sum' or lhs.name == 'wsum' or lhs.name == "sub")):
# a BoundedLinearExpression LHS, special case, like in objective
grblhs = self._make_numexpr(lhs)
self.grb_model.addLConstr(grblhs, GRB.EQUAL, grbrhs)
self.cons.append([self.grb_model.addLConstr(grblhs, GRB.EQUAL, grbrhs), cpm_expr_orig])

elif lhs.name == 'mul':
assert len(lhs.args) == 2, "Gurobi only supports multiplication with 2 variables"
a, b = self.solver_vars(lhs.args)
self.grb_model.setParam("NonConvex", 2)
self.grb_model.addConstr(a * b == grbrhs)
self.cons.append([self.grb_model.setParam("NonConvex", 2), cpm_expr_orig])
self.cons.append([self.grb_model.addConstr(a * b == grbrhs), cpm_expr_orig])

elif lhs.name == 'div':
assert is_num(lhs.args[1]), "Gurobi only supports division by constants"
a, b = self.solver_vars(lhs.args)
self.grb_model.addLConstr(a / b, GRB.EQUAL, grbrhs)
self.cons.append([self.grb_model.addLConstr(a / b, GRB.EQUAL, grbrhs), cpm_expr_orig])

else:
# General constraints
Expand All @@ -342,15 +344,15 @@ def __add__(self, cpm_expr_orig):
grbrhs = self.solver_var(intvar(lb=grbrhs, ub=grbrhs))

if lhs.name == 'min':
self.grb_model.addGenConstrMin(grbrhs, self.solver_vars(lhs.args))
self.cons.append([self.grb_model.addGenConstrMin(grbrhs, self.solver_vars(lhs.args)), cpm_expr_orig])
elif lhs.name == 'max':
self.grb_model.addGenConstrMax(grbrhs, self.solver_vars(lhs.args))
self.cons.append([self.grb_model.addGenConstrMax(grbrhs, self.solver_vars(lhs.args)), cpm_expr_orig])
elif lhs.name == 'abs':
self.grb_model.addGenConstrAbs(grbrhs, self.solver_var(lhs.args[0]))
self.cons.append([self.grb_model.addGenConstrAbs(grbrhs, self.solver_var(lhs.args[0])), cpm_expr_orig])
elif lhs.name == 'pow':
x, a = self.solver_vars(lhs.args)
assert a == 2, "Gurobi: 'pow', only support quadratic constraints (x**2)"
self.grb_model.addGenConstrPow(x, grbrhs, a)
self.cons.append([self.grb_model.addGenConstrPow(x, grbrhs, a), cpm_expr_orig])
else:
raise NotImplementedError(
"Not a known supported gurobi comparison '{}' {}".format(lhs.name, cpm_expr))
Expand All @@ -375,27 +377,39 @@ def __add__(self, cpm_expr_orig):
else:
raise Exception(f"Unknown linear expression {lhs} on right side of indicator constraint: {cpm_expr}")
if sub_expr.name == "<=":
self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.LESS_EQUAL, self.solver_var(rhs))
self.cons.append([self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.LESS_EQUAL, self.solver_var(rhs)), cpm_expr_orig])
elif sub_expr.name == ">=":
self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.GREATER_EQUAL, self.solver_var(rhs))
self.cons.append([self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.GREATER_EQUAL, self.solver_var(rhs)), cpm_expr_orig])
elif sub_expr.name == "==":
self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.EQUAL, self.solver_var(rhs))
self.cons.append([self.grb_model.addGenConstrIndicator(cond, bool_val, lin_expr, GRB.EQUAL, self.solver_var(rhs)), cpm_expr_orig])
else:
raise Exception(f"Unknown linear expression {sub_expr} name")

# True or False
elif isinstance(cpm_expr, BoolVal):
self.grb_model.addConstr(cpm_expr.args[0])
self.cons.append([self.grb_model.addConstr(cpm_expr.args[0]), cpm_expr_orig])

# a direct constraint, pass to solver
elif isinstance(cpm_expr, DirectConstraint):
cpm_expr.callSolver(self, self.grb_model)
self.cons.append([cpm_expr.callSolver(self, self.grb_model), cpm_expr_orig])

else:
raise NotImplementedError(cpm_expr) # if you reach this... please report on github

return self


def __sub__(self, cpm_expr_orig):

for c in self.cons:
if c[1] == cpm_expr_orig:
print(c[0])
self.grb_model.remove(c[0])
self.cons.remove(c)
print("asflwbha;ekfwgaerbfgar")

return self

def solveAll(self, display=None, time_limit=None, solution_limit=None, call_from_model=False, **kwargs):
"""
Compute all solutions and optionally display the solutions.
Expand Down

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