def solve_cylp(self, verbose: bool = True, **kwargs):
""" Inspired by the cvxpy cbc layer, ty :) """
from cylp.cy import CyClpSimplex
from cylp.py.modeling.CyLPModel import CyLPModel, CyLPArray
cons = self.combine_cons()
n = int(self.next_var_idx - 1) # Number of variables.
# Maximize c@x s.t. A@x <= b (variable bounds done by constraints)
c = self.objective.rawdense().squeeze()[
1:n + 1] # Objective coefficients, no constants.
A = cons.raw()[:, 1:n + 1] # Constraint coefficients.
b = cons[:, 0].rawdense().squeeze() * -1.0 # Constraint constants.
model = CyLPModel()
x = model.addVariable("x", n) # Variables
model.objective = c
# I hate this so much. Casting A to a matrix causes A.__mul__ to be
# be called, which raises NotImplemented, so then x.__rmul__ is called
# which gets the job done. Using np.matmul or np.dot doesn't
# trigger x.__rmul__
# model.addConstraint(np.matrix(A) * x <= CyLPArray(b)) # Works
model.addConstraint(x.__rmul__(A) <= CyLPArray(b))
model = CyClpSimplex(model) # Convert model
model.logLevel = 0 if not verbose else model.logLevel
is_integer_model = not np.isclose(self.int_vars.sum(), 0)
if is_integer_model:
model.setInteger(x[np.argwhere(self.int_vars)])
cbcModel = model.getCbcModel()
cbcModel.solve()
status = cbcModel.status
solmodel = cbcModel
else:
status = model.initialSolve()
solmodel = model
sol_x = np.hstack( # Pad back to original shape
(
[1.0], # Special constant 1.0 variable.
solmodel.primalVariableSolution["x"], # Actual solution
np.zeros(self.max_vars - n - 1), # Unused vars
))
solution = {
"status": status,
"primal": sol_x,
"value": solmodel.objectiveValue
}
return solution, solution["primal"]
def solve(self, objective, constraints, cached_data,
warm_start, verbose, solver_opts):
"""Returns the result of the call to the solver.
Parameters
----------
objective : LinOp
The canonicalized objective.
constraints : list
The list of canonicalized cosntraints.
cached_data : dict
A map of solver name to cached problem data.
warm_start : bool
Not used.
verbose : bool
Should the solver print output?
solver_opts : dict
Additional arguments for the solver.
Returns
-------
tuple
(status, optimal value, primal, equality dual, inequality dual)
"""
# Import basic modelling tools of cylp
from cylp.cy import CyClpSimplex
from cylp.py.modeling.CyLPModel import CyLPModel, CyLPArray
# Get problem data
data = self.get_problem_data(objective, constraints, cached_data)
c = data[s.C]
b = data[s.B]
A = data[s.A]
dims = data[s.DIMS]
data[s.BOOL_IDX] = solver_opts[s.BOOL_IDX]
data[s.INT_IDX] = solver_opts[s.INT_IDX]
n = c.shape[0]
# Problem
model = CyLPModel()
# Variables
x = model.addVariable('x', n)
# Constraints
# eq
model += A[0:dims[s.EQ_DIM], :] * x == CyLPArray(b[0:dims[s.EQ_DIM]])
# leq
leq_start = dims[s.EQ_DIM]
leq_end = dims[s.EQ_DIM] + dims[s.LEQ_DIM]
model += A[leq_start:leq_end, :] * x <= CyLPArray(b[leq_start:leq_end])
# Objective
model.objective = c
# Convert model
model = CyClpSimplex(model)
# No boolean vars available in Cbc -> model as int + restrict to [0,1]
if self.is_mip(data):
# Mark integer- and binary-vars as "integer"
model.setInteger(x[data[s.BOOL_IDX]])
model.setInteger(x[data[s.INT_IDX]])
# Restrict binary vars only
idxs = data[s.BOOL_IDX]
n_idxs = len(idxs)
model.setColumnLowerSubset(np.arange(n_idxs, dtype=np.int32),
np.array(idxs, np.int32),
np.zeros(n_idxs))
model.setColumnUpperSubset(np.arange(n_idxs, dtype=np.int32),
np.array(idxs, np.int32),
np.ones(n_idxs))
# Verbosity Clp
if not verbose:
model.logLevel = 0
# Build model & solve
status = None
if self.is_mip(data):
# Convert model
cbcModel = model.getCbcModel()
# Verbosity Cbc
if not verbose:
cbcModel.logLevel = 0
# cylp: /cylp/cy/CyCbcModel.pyx#L134
# Call CbcMain. Solve the problem using the same parameters used by
# CbcSolver. Equivalent to solving the model from the command line
# using cbc's binary.
cbcModel.solve()
status = cbcModel.status
else:
# cylp: /cylp/cy/CyClpSimplex.pyx
# Run CLP's initialSolve. It does a presolve and uses primal or dual
# Simplex to solve a problem.
status = model.initialSolve()
results_dict = {}
results_dict["status"] = status
if self.is_mip(data):
results_dict["x"] = cbcModel.primalVariableSolution['x']
results_dict["obj_value"] = cbcModel.objectiveValue
else:
results_dict["x"] = model.primalVariableSolution['x']
results_dict["obj_value"] = model.objectiveValue
return self.format_results(results_dict, data, cached_data)
def solve_via_data(self, data, warm_start, verbose, solver_opts, solver_cache=None):
# Import basic modelling tools of cylp
from cylp.cy import CyClpSimplex
from cylp.py.modeling.CyLPModel import CyLPModel, CyLPArray
c = data[s.C]
b = data[s.B]
A = data[s.A]
dims = dims_to_solver_dict(data[s.DIMS])
n = c.shape[0]
# Problem
model = CyLPModel()
# Variables
x = model.addVariable('x', n)
# Constraints
# eq
model += A[0:dims[s.EQ_DIM], :] * x == CyLPArray(b[0:dims[s.EQ_DIM]])
# leq
leq_start = dims[s.EQ_DIM]
leq_end = dims[s.EQ_DIM] + dims[s.LEQ_DIM]
model += A[leq_start:leq_end, :] * x <= CyLPArray(b[leq_start:leq_end])
# Objective
model.objective = c
# Convert model
model = CyClpSimplex(model)
# No boolean vars available in Cbc -> model as int + restrict to [0,1]
if data[s.BOOL_IDX] or data[s.INT_IDX]:
# Mark integer- and binary-vars as "integer"
model.setInteger(x[data[s.BOOL_IDX]])
model.setInteger(x[data[s.INT_IDX]])
# Restrict binary vars only
idxs = data[s.BOOL_IDX]
n_idxs = len(idxs)
model.setColumnLowerSubset(np.arange(n_idxs, dtype=np.int32),
np.array(idxs, np.int32),
np.zeros(n_idxs))
model.setColumnUpperSubset(np.arange(n_idxs, dtype=np.int32),
np.array(idxs, np.int32),
np.ones(n_idxs))
# Verbosity Clp
if not verbose:
model.logLevel = 0
# Build model & solve
status = None
if data[s.BOOL_IDX] or data[s.INT_IDX]:
# Convert model
cbcModel = model.getCbcModel()
for key, value in solver_opts.items():
setattr(cbcModel, key, value)
# Verbosity Cbc
if not verbose:
cbcModel.logLevel = 0
# cylp: /cylp/cy/CyCbcModel.pyx#L134
# Call CbcMain. Solve the problem using the same parameters used by
# CbcSolver. Equivalent to solving the model from the command line
# using cbc's binary.
cbcModel.solve()
status = cbcModel.status
else:
# cylp: /cylp/cy/CyClpSimplex.pyx
# Run CLP's initialSolve. It does a presolve and uses primal or dual
# Simplex to solve a problem.
status = model.initialSolve()
solution = {}
if data[s.BOOL_IDX] or data[s.INT_IDX]:
solution["status"] = self.STATUS_MAP_MIP[status]
solution["primal"] = cbcModel.primalVariableSolution['x']
solution["value"] = cbcModel.objectiveValue
else:
solution["status"] = self.STATUS_MAP_LP[status]
solution["primal"] = model.primalVariableSolution['x']
solution["value"] = model.objectiveValue
return solution
