def build_dqm(W, C, n, p, a, verbose=True):
"""Builds discrete quadratic model representing the optimization problem.
Args:
- W: Numpy matrix. Represents passenger demand. Normalized with total demand equal to 1.
- C: Numpy matrix. Represents airline leg cost.
- n: Int. Number of cities in play.
- p: Int. Number of hubs airports allowed.
- a: Float in [0.0, 1.0]. Discount allowed for hub-hub legs.
- verbose: Print to command-line for user.
Returns:
- dqm: DiscreteQuadraticModel representing the optimization problem.
"""
if verbose:
print("\nBuilding DQM...\n")
# Initialize DQM object.
dqm = DiscreteQuadraticModel()
for i in range(n):
dqm.add_variable(n, label=i)
# Objective: Minimize cost.
for i in range(n):
for j in range(n):
for k in range(n):
dqm.set_linear_case(
i, k,
dqm.get_linear_case(i, k) + C[i][k] * W[i][j])
dqm.set_linear_case(
j, k,
dqm.get_linear_case(j, k) + C[j][k] * W[i][j])
for m in range(n):
if i != j:
dqm.set_quadratic_case(i, k, j, m,
a * C[k][m] * W[i][j])
# Constraint: Every leg must connect to a hub.
gamma1 = 150
for i in range(n):
for j in range(n):
if i != j:
dqm.set_linear_case(i, j,
dqm.get_linear_case(i, j) + 1 * gamma1)
dqm.set_quadratic_case(
i, j, j, j,
dqm.get_quadratic_case(i, j, j, j) - 1 * gamma1)
# Constraint: Exactly p hubs required.
gamma2 = 250
for i in range(n):
dqm.set_linear_case(i, i,
dqm.get_linear_case(i, i) + (1 - 2 * p) * gamma2)
for j in range(i + 1, n):
dqm.set_quadratic_case(
i, i, j, j,
dqm.get_quadratic_case(i, i, j, j) + 2 * gamma2)
return dqm
def solve(adj_nodes, adj_edges, even_dist=False):
dqm = DiscreteQuadraticModel()
for i in adj_nodes:
dqm.add_variable(NURSES, label=i)
# classic graph coloring constraint that no two adjacent nodes have the same color
for i0, i1 in adj_edges:
dqm.set_quadratic(i0, i1, {(c, c): LAGRANGE for c in range(NURSES)})
shifts_per_nurse = DAYS * SHIFTS // NURSES
if even_dist:
# we should ensure that nurses get assigned a roughly equal amount of work
for i in range(NURSES):
for index, j in enumerate(adj_nodes):
dqm.set_linear_case(
j, i,
dqm.get_linear_case(j, i) - LAGRANGE *
(2 * shifts_per_nurse + 1))
for k_index in range(index + 1, len(adj_nodes)):
k = adj_nodes[k_index]
dqm.set_quadratic_case(
j, i, k, i,
LAGRANGE * (dqm.get_quadratic_case(j, i, k, i) + 2))
# some nurses may hate each other, so we should do out best to not put them in the same shift!
for d in range(DAYS):
for s in range(SHIFTS):
for l1 in range(NURSES_PER_SHIFT):
for l2 in range(l1 + 1, NURSES_PER_SHIFT):
j = f"l{l1}_d{d}_s{s}"
k = f"l{l2}_d{d}_s{s}"
for conflict in CONFLICTS:
for n1 in conflict:
for n2 in conflict:
if n1 == n2:
continue
dqm.set_quadratic_case(
j, n1, k, n2,
LAGRANGE2 *
(dqm.get_quadratic_case(j, n1, k, n2) +
10))
sampler = LeapHybridDQMSampler(token=API_TOKEN)
sampleset = sampler.sample_dqm(dqm, time_limit=10)
sample = sampleset.first.sample
energy = sampleset.first.energy
return sample, energy
preferences = preferences[rows, cols]
# Initialize the DQM object
dqm = DiscreteQuadraticModel()
# Build the DQM starting by adding variables
for name in range(num_employees):
dqm.add_variable(num_shifts, label=name)
# Distribute employees equally across shifts according to preferences
num_per_shift = int(num_employees/num_shifts)
gamma = 1/(num_employees*num_shifts)
for i in range(num_shifts):
for j in range(num_employees):
dqm.set_linear_case(j, i, dqm.get_linear_case(j, i) - gamma*(2*num_per_shift+1))
for k in range(j+1, num_employees):
dqm.set_quadratic_case(j, i, k, i, gamma*(dqm.get_quadratic_case(j, i, k, i) + 2))
# Initialize the DQM solver
sampler = LeapHybridDQMSampler()
# Solve the problem using the DQM solver
sampleset = sampler.sample_dqm(dqm, label='Example - Employee Scheduling')
# Get the first solution, and print it
# Mi da la soluzione migliore, quella in cui sono caduto più volte e me la salvo
sample = sampleset.first.sample
energy = sampleset.first.energy
print("\nSchedule score:", energy)