def solve(Ma, Mw):
write_graph(Ma, Mw, [], 'tmp', int_weights=True)
redirector_stdout = Redirector(fd=STDOUT)
redirector_stderr = Redirector(fd=STDERR)
redirector_stderr.start()
redirector_stdout.start()
solver = TSPSolver.from_tspfile('tmp')
solution = solver.solve(verbose=False)
redirector_stderr.stop()
redirector_stdout.stop()
return solution.tour if solution.found_tour else []
def solve(Ma, Mw):
"""
Invokes Concorde to solve a TSP instance
Uses Python's Redirector library to prevent Concorde from printing
unsufferably verbose messages
"""
STDOUT = 1
STDERR = 2
redirector_stdout = Redirector(fd=STDOUT)
redirector_stderr = Redirector(fd=STDERR)
# Write graph on a temporary file
write_graph(Ma, Mw, filepath='tmp', int_weights=True)
redirector_stderr.start()
redirector_stdout.start()
# Solve TSP on graph
solver = TSPSolver.from_tspfile('tmp')
# Get solution
solution = solver.solve(verbose=False)
redirector_stderr.stop()
redirector_stdout.stop()
"""
Concorde solves only symmetric TSP instances. To circumvent this, we
fill inexistent edges with large weights. Concretely, an inexistent
edge is assigned with the strictest upper limit to the cost of an
optimal tour, which is n (the number of nodes) times 1 (the maximum weight).
If one of these edges is used in the optimal solution, we can deduce
that no valid tour exists (as just one of these edges costs more than
all the others combined).
OBS. in this case the maximum weight 1 is multiplied by 'bins' because
we are converting from floating point to integers
"""
if any([
Ma[i, j] == 0
for (i,
j) in zip(list(solution.tour),
list(solution.tour)[1:] + list(solution.tour)[:1])
]):
return None
else:
return list(solution.tour)
