def generateCuts(self, si, cglTreeInfo):
m = self.cyLPModel
x = m.getVarByName('x')
clpModel = si.clpModel
clpModel.dual(startFinishOptions='x')
solution = clpModel.primalVariableSolution
bv = clpModel.basicVariables
rhs = clpModel.rhs
intInds = clpModel.integerInformation
rhsIsInt = list(map(isInt, rhs))
cuts = []
for rowInd in range(s.nConstraints):
basicVarInd = bv[rowInd]
if basicVarInd < clpModel.nVariables and intInds[
basicVarInd] and not rhsIsInt[rowInd]:
coef, b = gomoryCut(clpModel, rowInd)
if b is not None:
#print 'Adding cut: ', coef, '>=', b
expr = CyLPArray(coef) * x >= b
cuts.append(expr)
return cuts
def generateQP(self):
m = self.m
n = self.n
s = CyClpSimplex()
iNonZero = set(random.randint(n, size=self.nnzPerCol))
iZero = [i for i in range(n) if i not in iNonZero]
x_star = np.matrix(np.zeros((n, 1)))
z_star = np.matrix(np.zeros((n, 1)))
for i in iNonZero:
x_star[i, 0] = 1
for i in iZero:
z_star[i, 0] = 0 if random.randint(2) else random.random()
G = getG(n)
A = getA(m, n, self.nnzPerCol)
y_star = np.matrix(random.random((m, 1)))
c = -(G * x_star - A.T * y_star - z_star)
obj = 0.5 * ((x_star.T * G) * x_star) + c.T * x_star
print(obj)
c = CyLPArray((c.T)[0])
b = CyLPArray(((A * x_star).T)[0])
b = np.squeeze(np.asarray(b))
x = s.addVariable('x', n)
s += A * x == b
s += x >= 0
c = CyLPArray(c)
s.objective = c * x
s.Hessian = G
self.model = s
return s
#print 'Adding cut: ', coef, '>=', b
expr = CyLPArray(coef) * x >= b
cuts.append(expr)
return cuts
if __name__ == '__main__':
m = CyLPModel()
firstExample = False
if (firstExample):
x = m.addVariable('x', 2, isInt=True)
A = np.matrix([[7., -2.], [0., 1], [2., -2]])
b = CyLPArray([14, 3, 3])
m += A * x <= b
m += x >= 0
c = CyLPArray([-4, 1])
m.objective = c * x
s = CyClpSimplex(m)
else:
s = CyClpSimplex()
#cylpDir = os.environ['CYLP_SOURCE_DIR']
inputFile = os.path.join('..', '..', 'input', 'p0033.mps')
m = s.extractCyLPModel(inputFile)
x = m.getVarByName('x')
s.setInteger(x)
def solve(m, whichCuts = [],
debug_print = False, epsilon = .01,
max_iter = 100, max_cuts = 10, display = False):
if not isinstance(m, MILPInstance):
raise "Invalid first parameter: Must be of type MILPInstance"
if not DISPLAY_ENABLED:
display = False
if m.lp.nCols > 2 or m.A is None:
display = False
m.lp.logLevel = 0
if display:
disp_relaxation(m.A, m.b)
for i in xrange(max_iter):
print 'Iteration ', i
m.lp.primal(startFinishOptions = 'x')
print 'Current bound:', m.lp.objectiveValue
#Binv = np.zeros(shape = (lp.nConstraints, lp.nConstraints))
#for i in range(lp.nVariables, lp.nVariables+lp.nConstraints):
# lp.getBInvACol(i, Binv[i-lp.nVariables,:])
#rhs = lp.rhs
if m.sense == '<=':
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsUpper)
else:
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsLower)
sol = m.lp.primalVariableSolution['x']
if debug_print:
print 'Current basis inverse:'
print m.lp.basisInverse
print 'Condition number of basis inverse'
print np.linalg.cond(m.lp.basisInverse)
print "Current tableaux:"
print m.lp.tableau
print "Current right hand side:\n", rhs
#print lp.rhs
print 'Current solution: ', sol
if isInt(sol[m.integerIndices], epsilon):
print 'Integer solution found!'
break
cuts = []
disj = []
for (cg, args) in whichCuts:
tmp_cuts, tmp_disj = cg(m.lp, m.integerIndices, m.sense, sol, **args)
cuts += tmp_cuts
disj += tmp_disj
if cuts == []:
print 'No cuts found!'
break
if display:
disp_relaxation(m.A, m.b, cuts, sol, disj)
for (coeff, r) in cuts[:max_cuts]:
#TODO sort cuts by degree of violation
if m.sense == '<=':
print 'Adding cut: ', coeff, '<=', r
m.lp += CyLPArray(coeff) * m.x <= r
else:
print 'Adding cut: ', coeff, '>=', r
m.lp += CyLPArray(coeff) * m.x >= r
if display:
m.A.append(coeff.tolist())
m.b.append(r)
if display:
disp_relaxation(m.A, m.b)
def __init__(self,
module_name=None,
file_name=None,
A=None,
b=None,
c=None,
points=None,
rays=None,
sense=None,
integerIndices=None,
numVars=None):
if file_name is not None:
# We got a file name, so ignore everything else and read in the instance
lp = CyClpSimplex()
lp.extractCyLPModel(file_name)
self.integerIndices = [
i for (i, j) in enumerate(lp.integerInformation) if j == True
]
infinity = lp.getCoinInfinity()
A = lp.coefMatrix
b = CyLPArray([0 for _ in range(lp.nRows)])
for i in range(lp.nRows):
if lp.constraintsLower[i] > -infinity:
if lp.constraintsUpper[i] < infinity:
raise Exception('Cannot handle ranged constraints')
b[i] = -lp.constraintsLower[i]
for j in range(lp.nCols):
A[i, j] = -A[i, j]
elif lp.constraintsUpper[i] < infinity:
b[i] = lp.constraintsUpper[i]
else:
raise Exception('Constraint with no bounds detected')
x = lp.addVariable('x', lp.nCols)
lp += A * x <= b
lp += x <= lp.variablesUpper
lp += x >= lp.variablesLower
lp.objective = lp.objective
self.sense = '<='
numVars = lp.nCols
else:
min_or_max = None
if module_name is not None:
# We got a module name, read the data from there
mip = ilib.import_module(module_name)
self.A = mip.A if hasattr(mip, 'A') else None
self.b = mip.b if hasattr(mip, 'b') else None
points = mip.points if hasattr(mip, 'points') else None
rays = mip.rays if hasattr(mip, 'rays') else None
self.c = mip.c if hasattr(mip, 'c') else None
self.sense = mip.sense[1] if hasattr(mip, 'sense') else None
min_or_max = mip.sense[0] if hasattr(mip, 'sense') else None
self.integerIndices = mip.integerIndices if hasattr(
mip, 'integerIndices') else None
x_u = CyLPArray(mip.x_u) if hasattr(mip, 'x_u') else None
numVars = mip.numVars if hasattr(mip, 'numVars') else None
self.x_sep = mip.x_sep if hasattr(mip, 'x_sep') else None
if numVars is None and mip.A is not None:
numVars = len(mip.A)
if numVars is None:
raise "Must specify number of variables when problem is not"
else:
self.A = A
self.b = b
self.c = c
self.points = points
self.rays = rays
if sense is not None:
self.sense = sense[1]
min_or_max = sense[0]
self.integerIndices = integerIndices
x_u = None
lp = CyClpSimplex()
if self.A is not None:
A = np.matrix(self.A)
b = CyLPArray(self.b)
elif numVars <= 2 and GRUMPY_INSTALLED:
p = Polyhedron2D(points=points, rays=rays)
A = np.matrix(p.hrep.A)
b = np.matrix(p.hrep.b)
else:
raise "Must specify problem in inequality form with more than two variables\n"
#Warning: At the moment, you must put bound constraints in explicitly for split cuts
x_l = CyLPArray([0 for _ in range(numVars)])
x = lp.addVariable('x', numVars)
lp += x >= x_l
if x_u is not None:
lp += x <= x_u
lp += (A * x <= b if self.sense == '<=' else A * x >= b)
c = CyLPArray(self.c)
if min_or_max == 'Max':
lp.objective = -c * x
else:
lp.objective = c * x
self.lp = lp
self.x = x
try:
p = Polyhedron2D(A=LP.A, b=LP.b)
except AttributeError:
try:
p = Polyhedron2D(points=LP.points, rays=LP.rays)
except AttributeError:
print 'Error: Must specify either A and b or points and rays'
p = None
if p is not None:
if CYLP_INSTALLED:
lp = CyClpSimplex()
A = np.matrix(p.hrep.A)
b = CyLPArray(p.hrep.b)
print A
print b
if LP.numVars == 2:
disp_polyhedron(A=A, b=b)
x = lp.addVariable('x', LP.numVars)
if LP.sense[0] == '>=':
lp += A * x >= b
else:
lp += A * x <= b
#lp += x >= 0
def solve(m,
whichCuts=[],
use_cglp=False,
debug_print=False,
eps=EPS,
max_iter=100,
max_cuts=10,
display=False,
filename=None):
if not isinstance(m, MILPInstance):
print("Invalid first parameter: Must be of type MILPInstance")
exit
if not DISPLAY_ENABLED:
display = False
else:
f = Figure()
if m.lp.nCols > 2 or m.A is None:
display = False
m.lp.logLevel = 0
#Include bounds explicitly in the constraint matrix for display and for
#use in cut generators.
infinity = m.lp.getCoinInfinity()
if m.sense == '<=':
b = m.lp.constraintsUpper.copy()
mult = -1.0
else:
b = m.lp.constraintsLower.copy()
mult = 1.0
if type(m.A) == csc_matrixPlus:
A = m.A.toarray()
else:
A = m.A.copy()
for i in range(m.lp.nCols):
e = np.zeros((1, m.lp.nCols))
if m.lp.variablesUpper[i] < infinity:
b.resize(b.size + 1, refcheck=False)
e[0, i] = -mult
b[-1] = -mult * m.lp.variablesUpper[i]
A = np.vstack((A, e))
if m.lp.variablesLower[i] > -infinity:
b.resize(b.size + 1, refcheck=False)
e[0, i] = mult
b[-1] = mult * m.lp.variablesLower[i]
A = np.vstack((A, e))
m.A = A
m.b = b
if display and filename is not None:
disp_relaxation(f, m.A, m.b, filename=filename + '.png')
elif display:
disp_relaxation(f, m.A, m.b)
disj = []
prev_sol = np.zeros((1, m.lp.nCols))
for i in range(max_iter):
print('Iteration ', i)
m.lp.primal(startFinishOptions='x')
print('Current bound:', m.lp.objectiveValue)
#Binv = np.zeros(shape = (lp.nConstraints, lp.nConstraints))
#for i in range(lp.nVariables, lp.nVariables+lp.nConstraints):
# lp.getBInvACol(i, Binv[i-lp.nVariables,:])
#rhs = lp.rhs
if m.sense == '<=':
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsUpper)
else:
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsLower)
sol = m.lp.primalVariableSolution['x']
if debug_print:
print('Current basis inverse:')
print(m.lp.basisInverse)
print('Condition number of basis inverse',
np.around(np.linalg.cond(m.lp.basisInverse)))
print('Current tableaux:')
print(m.lp.tableau)
print('Current right hand side:\n', rhs)
#print('Dual solution:', m.lp.dualConstraintSolution)
#print lp.rhs
print('Current solution: ', sol)
if (sol - prev_sol).any():
prev_sol = sol
else:
print("Solution repeated, stalling detected")
print("Exiting")
break
if isInt(sol[m.integerIndices], eps):
print('Integer solution found!')
break
if np.around(np.linalg.cond(m.lp.basisInverse)) >= 10**32:
print("Condition number of the basis matrix exceeds 10^32")
print("Exiting")
break
cuts = []
if disj == []:
for (cg, args) in whichCuts:
tmp_cuts, tmp_disj = cg(m, **args, eps=eps)
cuts += tmp_cuts
disj += tmp_disj
cur_num_cuts = len(cuts)
if use_cglp:
if len(disj) > 0:
for d in disj:
cuts += disjunctionToCut(m, d[0], d[1], eps=eps)
if cuts == []:
if disj == []:
print('No cuts found and terminating!')
break
else:
print('No cuts found but continuing!')
if display and filename is not None:
disp_relaxation(f,
m.A,
m.b,
cuts,
sol,
disj,
filename=filename + str(i) + '.png')
elif display:
disp_relaxation(f, m.A, m.b, cuts, sol, disj)
if len(cuts) == cur_num_cuts:
disj = []
for (coeff, r) in cuts[:max_cuts]:
#TODO sort cuts by degree of violation
if m.sense == '<=':
coeff = np.floor(coeff * (10**eps)) / (10**eps)
r = np.ceil(r * (10**eps)) / (10**eps)
print('Adding cut: ', coeff, '<=', r)
m.lp += CyLPArray(coeff) * m.x <= r
else:
coeff = np.ceil(coeff * (10**eps)) / (10**eps)
r = np.floor(r * (10**eps)) / (10**eps)
print('Adding cut: ', coeff, '>=', r)
m.lp += CyLPArray(coeff) * m.x >= r
m.A = np.vstack((m.A, np.array(coeff)))
m.b.resize(m.b.size + 1, refcheck=False)
m.b[-1] = r
if display:
disp_relaxation(f, m.A, m.b)
def disjunctionToCut(m, pi, pi0, debug_print=False, use_cylp=True, eps=EPS):
'''Generate the most violated valid inequality from a given disjunction'''
me = "cglp_cuts: "
lp = m.lp
sol = lp.primalVariableSolution['x']
if debug_print:
print(me, "constraints sense = ", m.sense)
print(me, "matrix = ")
print(m.A)
print(me, "rhs = ", m.b)
print(me, "vars lower bounds = ", lp.variablesLower)
print(me, "vars upper bounds = ", lp.variablesUpper)
print(me, "objective = ", lp.objective)
print(me, "current solution = ", sol)
print(me, "pi = ", pi)
print(me, "pi0 = ", pi0)
############################################################################
## There are two given LPs:
## s.t. Ax >= b s.t. Ax >= b
## -pi.x >= -pi_0 pi.x >= pi_0+1
## A, b, c, pi, pi_0 are given
##
## CGLP: alpha.x >= beta should be valid for both LPs above
##
## min alpha.x* - beta
## uA - u0.pi = alpha
## vA + v0.pi = alpha
## ub - u0.pi_0 >= beta
## vb + v0.(pi_0 + 1) >= beta
## u0 + v0 = 1
## u, v, u0, v0 >= 0
## if min value comes out < 0, then (alpha.x >= beta) is a cut.
############################################################################
pi = CyLPArray(pi)
Atran = m.A.transpose()
b = CyLPArray(m.b)
numRows, numCols = m.A.shape
if use_cylp:
sp = CyLPModel()
u = sp.addVariable('u', numRows, isInt=False)
v = sp.addVariable('v', numRows, isInt=False)
u0 = sp.addVariable('u0', 1, isInt=False)
v0 = sp.addVariable('v0', 1, isInt=False)
alpha = sp.addVariable('alpha', lp.nVariables, isInt=False)
beta = sp.addVariable('beta', 1, isInt=False)
#This should be as simple as this, but it doesn't work.
#Maybe a bug in CyLP?
#sp += alpha - Atran*u - pi*u0 == 0
#sp += alpha - Atran*v + pi*v0 == 0
for i in range(numCols):
sp += alpha[i] - sum(Atran[i, j] * u[j]
for j in range(numRows)) - pi[i] * u0 == 0
for i in range(numCols):
sp += alpha[i] - sum(Atran[i, j] * v[j]
for j in range(numRows)) + pi[i] * v0 == 0
if m.sense == '<=':
sp += beta - b * u - pi0 * u0 >= 0
sp += beta - b * v + (pi0 + 1) * v0 >= 0
else:
sp += beta - b * u - pi0 * u0 <= 0
sp += beta - b * v + (pi0 + 1) * v0 <= 0
sp += u0 + v0 == 1
sp += u >= 0
sp += v >= 0
sp += u0 >= 0
sp += v0 >= 0
if m.sense == '<=':
sp.objective = sum(-sol[i] * alpha[i]
for i in range(numCols)) + beta
else:
#This direction is not debugged
sp.objective = sum(sol[i] * alpha[i]
for i in range(numCols)) - beta
cglp = CyClpSimplex(sp)
# If we want to solve it as an MILP
# cglp = CyClpSimplex(sp).getCbcModel()
#cglp.writeLp('lp.lp')
cglp.logLevel = 0
cglp.primal(startFinishOptions='x')
# Solve as MILP
# cglp.solve()
beta = cglp.primalVariableSolution['beta'][0]
alpha = cglp.primalVariableSolution['alpha']
u = cglp.primalVariableSolution['u']
v = cglp.primalVariableSolution['v']
u0 = cglp.primalVariableSolution['u0'][0]
v0 = cglp.primalVariableSolution['v0'][0]
if debug_print:
print(me, 'Objective Value: ', cglp.objectiveValue)
if debug_print:
print(me, 'u: ', u)
print(me, 'v: ', v)
print(me, 'u0: ', u0)
print(me, 'v0: ', v0)
else:
CG = AbstractModel()
CG.u = Var(list(range(numRows)),
domain=NonNegativeReals,
bounds=(0.0, None))
CG.v = Var(list(range(numRows)),
domain=NonNegativeReals,
bounds=(0.0, None))
CG.u0 = Var(domain=NonNegativeReals, bounds=(0.0, None))
CG.v0 = Var(domain=NonNegativeReals, bounds=(0.0, None))
CG.alpha = Var(list(range(numRows)), domain=Reals, bounds=(None, None))
CG.beta = Var(domain=Reals, bounds=(None, None))
## Constraints
def pi_rule_left(CG, i):
x = float(pi[i])
return (sum(Atran[i, j] * CG.u[j] for j in range(numRows)) -
x * CG.u0 - CG.alpha[i] == 0.0)
CG.pi_rule_left = Constraint(list(range(numCols)), rule=pi_rule_left)
def pi_rule_right(CG, i):
x = float(pi[i])
return (sum(Atran[i, j] * CG.v[j] for j in range(numRows)) +
x * CG.v0 - CG.alpha[i] == 0.0)
CG.pi_rule_right = Constraint(list(range(numCols)), rule=pi_rule_right)
if m.sense == '<=':
def pi0_rule_left(CG):
return (sum(b[j] * CG.u[j]
for j in range(numRows)) - pi0 * CG.u0 - CG.beta <=
0.0)
CG.pi0_rule_left = Constraint(rule=pi0_rule_left)
def pi0_rule_right(CG):
return (sum(b[j] * CG.v[j] for j in range(numRows)) +
(pi0 + 1) * CG.v0 - CG.beta <= 0.0)
CG.pi0_rule_right = Constraint(rule=pi0_rule_right)
else:
def pi0_rule_left(CG):
return (sum(b[j] * CG.u[j]
for j in range(numRows)) - pi0 * CG.u0 - CG.beta >=
0.0)
CG.pi0_rule_left = Constraint(rule=pi0_rule_left)
def pi0_rule_right(CG):
return (sum(b[j] * CG.v[j] for j in range(numRows)) +
(pi0 + 1) * CG.v0 - CG.beta >= 0.0)
CG.pi0_rule_right = Constraint(rule=pi0_rule_right)
def normalization_rule(CG):
return (CG.u0 + CG.v0 == 1.0)
CG.normalization_rule = Constraint(rule=normalization_rule)
def objective_rule(CG):
return (sum(sol[i] * CG.alpha[i]
for i in range(numCols)) - CG.beta)
if m.sense == '<=':
CG.objective = Objective(sense=maximize, rule=objective_rule)
else:
CG.objective = Objective(sense=minimize, rule=objective_rule)
opt = SolverFactory("cbc")
instance = CG.create_instance()
#instance.pprint()
#instance.write("foo.nl", format = "nl")
#opt.options['bonmin.bb_log_level'] = 5
#opt.options['bonmin.bb_log_interval'] = 1
results = opt.solve(instance, tee=False)
#results = opt.solve(instance)
instance.solutions.load_from(results)
beta = instance.beta.value
alpha = np.array(
[instance.alpha[i].value for i in range(lp.nVariables)])
violation = beta - np.dot(alpha, sol)
if debug_print:
print(me, 'Beta: ', beta)
print(me, 'alpha: ', alpha)
print(me, 'Violation of cut: ', violation)
if np.abs(violation) > 10**(-eps):
return [(alpha, beta)]
print('No violated cuts found solving CGLP', violation)
return []
def solve(m,
whichCuts=[],
use_cglp=False,
debug_print=False,
epsilon=.01,
max_iter=100,
max_cuts=10,
display=False):
if not isinstance(m, MILPInstance):
print("Invalid first parameter: Must be of type MILPInstance")
exit
if not DISPLAY_ENABLED:
display = False
if m.lp.nCols > 2 or m.A is None:
display = False
m.lp.logLevel = 0
if display:
disp_relaxation(m.A, m.b)
disj = []
for i in range(max_iter):
print('Iteration ', i)
m.lp.primal(startFinishOptions='x')
print('Current bound:', m.lp.objectiveValue)
#Binv = np.zeros(shape = (lp.nConstraints, lp.nConstraints))
#for i in range(lp.nVariables, lp.nVariables+lp.nConstraints):
# lp.getBInvACol(i, Binv[i-lp.nVariables,:])
#rhs = lp.rhs
if m.sense == '<=':
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsUpper)
else:
rhs = np.dot(m.lp.basisInverse, m.lp.constraintsLower)
sol = m.lp.primalVariableSolution['x']
if debug_print:
print('Current basis inverse:')
print(m.lp.basisInverse)
print('Condition number of basis inverse')
print(np.linalg.cond(m.lp.basisInverse))
print("Current tableaux:")
print(m.lp.tableau)
print("Current right hand side:\n", rhs)
#print lp.rhs
print('Current solution: ', sol)
if isInt(sol[m.integerIndices], epsilon):
print('Integer solution found!')
break
cuts = []
if disj == []:
for (cg, args) in whichCuts:
tmp_cuts, tmp_disj = cg(m.lp, m.integerIndices, m.sense, sol,
**args)
cuts += tmp_cuts
disj += tmp_disj
cur_num_cuts = len(cuts)
if use_cglp and len(disj) > 0:
for d in disj:
cuts += disjunctionToCut(m.lp, d[0], d[1], sense=m.sense)
if cuts == []:
if disj == []:
print('No cuts found and terminating!')
break
else:
print('No cuts found but continuing!')
if display:
disp_relaxation(m.A, m.b, cuts, sol, disj)
if len(cuts) == cur_num_cuts:
disj = []
for (coeff, r) in cuts[:max_cuts]:
#TODO sort cuts by degree of violation
if m.sense == '<=':
print('Adding cut: ', coeff, '<=', r)
m.lp += CyLPArray(coeff) * m.x <= r
else:
print('Adding cut: ', coeff, '>=', r)
m.lp += CyLPArray(coeff) * m.x >= r
if display:
m.A.append(coeff.tolist())
m.b.append(r)
if display:
disp_relaxation(m.A, m.b)
def disjunctionToCut(lp,
pi,
pi0,
integerIndices=None,
sense='>=',
sol=None,
debug_print=False,
use_cylp=True):
me = "cglp_cuts: "
if sol is None:
sol = lp.primalVariableSolution['x']
infinity = lp.getCoinInfinity()
if debug_print:
print(me, "constraints sense = ", sense)
print(me, "con lower bounds = ", lp.constraintsLower)
print(me, "con upper bounds = ", lp.constraintsUpper)
print(me, "con matrix = ", lp.coefMatrix.toarray())
print(me, "vars lower bounds = ", lp.variablesLower)
print(me, "vars upper bounds = ", lp.variablesUpper)
print(me, "Assuming objective is to minimize")
print(me, "objective = ", lp.objective)
print(me, "infinity = ", infinity)
print(me, "current point = ", sol)
print(me, "pi = ", pi)
print(me, "pi0 = ", pi0)
A = lp.coefMatrix.toarray()
#c = lp.objective
## Convert to >= if the problem is in <= form.
if sense == '<=':
b = deepcopy(lp.constraintsUpper)
b = -1.0 * b
A = -1.0 * A
else:
b = deepcopy(lp.constraintsLower)
#Add bounds on variables as explicit constraints
for i in range(lp.nCols):
e = np.zeros((1, lp.nCols))
if lp.variablesUpper[i] < infinity:
b.resize(b.size + 1, refcheck=False)
e[0, i] = -1.0
b[-1] = -1.0 * lp.variablesUpper[i]
A = np.vstack((A, e))
if lp.variablesLower[i] > -infinity:
b.resize(b.size + 1, refcheck=False)
e[0, i] = 1.0
b[-1] = lp.variablesLower[i]
A = np.vstack((A, e))
A = csc_matrixPlus(A)
############################################################################
## There are two given LPs:
## s.t. Ax >= b s.t. Ax >= b
## -pi.x >= -pi_0 pi.x >= pi_0+1
## A, b, c, pi, pi_0 are given
##
## CGLP: alpha.x >= beta should be valid for both LPs above
##
## min alpha.x* - beta
## uA - u0.pi = alpha
## vA + v0.pi = alpha
## ub - u0.pi_0 >= beta
## vb + v0.(pi_0 + 1) >= beta
## u0 + v0 = 1
## u, v, u0, v0 >= 0
## if min value comes out < 0, then (alpha.x >= beta) is a cut.
############################################################################
b = CyLPArray(b)
pi = CyLPArray(pi)
Atran = A.transpose()
if use_cylp:
sp = CyLPModel()
u = sp.addVariable('u', A.shape[0], isInt=False)
v = sp.addVariable('v', A.shape[0], isInt=False)
u0 = sp.addVariable('u0', 1, isInt=False)
v0 = sp.addVariable('v0', 1, isInt=False)
alpha = sp.addVariable('alpha', lp.nVariables, isInt=False)
beta = sp.addVariable('beta', 1, isInt=False)
for i in range(A.shape[1]):
sp += alpha[i] - sum(Atran[i, j] * u[j]
for j in range(A.shape[0])) + pi[i] * u0 == 0
for i in range(A.shape[1]):
sp += alpha[i] - sum(Atran[i, j] * v[j]
for j in range(A.shape[0])) - pi[i] * v0 == 0
sp += beta - b * u + pi0 * u0 <= 0
sp += beta - b * v - (pi0 + 1) * v0 <= 0
sp += u0 + v0 == 1
if sense == '<=':
sp += u >= 0
sp += v >= 0
sp += u0 >= 0
sp += v0 >= 0
else:
#TODO this direction is not debugged
# Is this all we need?
sp += u <= 0
sp += v <= 0
sp += u0 <= 0
sp += v0 <= 0
sp.objective = sum(sol[i] * alpha[i] for i in range(A.shape[1])) - beta
cbcModel = CyClpSimplex(sp).getCbcModel()
cbcModel.logLevel = 0
#cbcModel.maximumSeconds = 5
cbcModel.solve()
beta = cbcModel.primalVariableSolution['beta'][0]
alpha = cbcModel.primalVariableSolution['alpha']
u = cbcModel.primalVariableSolution['u']
v = cbcModel.primalVariableSolution['v']
u0 = cbcModel.primalVariableSolution['u0'][0]
v0 = cbcModel.primalVariableSolution['v0'][0]
if debug_print:
print('Objective Value: ', cbcModel.objectiveValue)
print('alpha: ', alpha, 'alpha*sol: ', np.dot(alpha, sol))
print('beta: ', beta)
print('Violation of cut: ', np.dot(alpha, sol) - beta)
else:
CG = AbstractModel()
CG.u = Var(list(range(A.shape[0])),
domain=NonNegativeReals,
bounds=(0.0, None))
CG.v = Var(list(range(A.shape[0])),
domain=NonNegativeReals,
bounds=(0.0, None))
CG.u0 = Var(domain=NonNegativeReals, bounds=(0.0, None))
CG.v0 = Var(domain=NonNegativeReals, bounds=(0.0, None))
CG.alpha = Var(list(range(A.shape[0])),
domain=Reals,
bounds=(None, None))
CG.beta = Var(domain=Reals, bounds=(None, None))
## Constraints
def pi_rule_left(CG, i):
x = float(pi[i])
return (sum(Atran[i, j] * CG.u[j] for j in range(A.shape[0])) -
x * CG.u0 - CG.alpha[i] == 0.0)
CG.pi_rule_left = Constraint(list(range(A.shape[1])),
rule=pi_rule_left)
def pi_rule_right(CG, i):
x = float(pi[i])
return (sum(Atran[i, j] * CG.v[j] for j in range(A.shape[0])) +
x * CG.v0 - CG.alpha[i] == 0.0)
CG.pi_rule_right = Constraint(list(range(A.shape[1])),
rule=pi_rule_right)
def pi0_rule_left(CG):
return (sum(b[j] * CG.u[j]
for j in range(A.shape[0])) - pi0 * CG.u0 - CG.beta >=
0.0)
CG.pi0_rule_left = Constraint(rule=pi0_rule_left)
def pi0_rule_right(CG):
return (sum(b[j] * CG.v[j] for j in range(A.shape[0])) +
(pi0 + 1) * CG.v0 - CG.beta >= 0.0)
CG.pi0_rule_right = Constraint(rule=pi0_rule_right)
def normalization_rule(CG):
return (CG.u0 + CG.v0 == 1.0)
CG.normalization_rule = Constraint(rule=normalization_rule)
def objective_rule(CG):
return (sum(sol[i] * CG.alpha[i]
for i in range(A.shape[1])) - CG.beta)
CG.objective = Objective(sense=minimize, rule=objective_rule)
opt = SolverFactory("cbc")
instance = CG.create_instance()
#instance.pprint()
#instance.write("foo.nl", format = "nl")
#opt.options['bonmin.bb_log_level'] = 5
#opt.options['bonmin.bb_log_interval'] = 1
results = opt.solve(instance, tee=False)
#results = opt.solve(instance)
instance.solutions.load_from(results)
beta = instance.beta.value
alpha = np.array(
[instance.alpha[i].value for i in range(lp.nVariables)])
violation = beta - np.dot(alpha, sol)
if debug_print:
print(me, 'Beta: ', beta)
print(me, 'alpha: ', alpha)
print(me, 'Violation of cut: ', violation)
if violation > 0.001:
if (sense == ">="):
return [(alpha, beta)]
else:
return [(-alpha, -beta)]
return []
