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add global constraint on incoming/outgoing literals

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Laurent Perron
2019-05-29 09:18:30 +02:00
parent 0c3be9a6d5
commit c8a556258f
1 changed files with 13 additions and 0 deletions
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13
examples/python/bus_driver_scheduling_sat.py
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@@ -164,6 +164,10 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
delay_literals = []
delay_weights = []
# Used to propagate more between drivers
shared_incoming_literals = collections.defaultdict(list)
shared_outgoing_literals = collections.defaultdict(list)
for d in range(num_drivers):
start_times.append(
model.NewIntVar(min_start_time - setup_time, max_end_time,
@@ -200,6 +204,7 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
source_lit = model.NewBoolVar('%i from source to %i' % (d, s))
outgoing_source_literals.append(source_lit)
incoming_literals[s].append(source_lit)
shared_incoming_literals[s].append(source_lit)
model.Add(start_times[d] == shift[3] -
setup_time).OnlyEnforceIf(source_lit)
model.Add(
@@ -213,6 +218,7 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
# - set the driving times of the driver
sink_lit = model.NewBoolVar('%i from %i to sink' % (d, s))
outgoing_literals[s].append(sink_lit)
shared_outgoing_literals[s].append(sink_lit)
incoming_sink_literals.append(sink_lit)
model.Add(end_times[d] == shift[4] +
cleanup_time).OnlyEnforceIf(sink_lit)
@@ -228,6 +234,8 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
performed[d, s].Not())
incoming_literals[s].append(performed[d, s].Not())
outgoing_literals[s].append(performed[d, s].Not())
# Not adding to the shared lists, because, globally, each node will have
# one incoming literal, and one outgoing literal.
# Node performed:
# - add upper bound on start_time
@@ -259,7 +267,9 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
# Add arc
outgoing_literals[s].append(lit)
shared_outgoing_literals[s].append(lit)
incoming_literals[o].append(lit)
shared_incoming_literals[o].append(lit)
# Cost part
delay_literals.append(lit)
@@ -296,6 +306,9 @@ def bus_driver_scheduling(minimize_drivers, max_num_drivers):
# Each shift is covered.
for s in range(num_shifts):
model.Add(sum(performed[d, s] for d in range(num_drivers)) == 1)
# Globally, each node has one incoming and one outgoing literal
model.Add(sum(shared_incoming_literals[s]) == 1)
model.Add(sum(shared_outgoing_literals[s]) == 1)
# Symmetry breaking