examples/notebook/sat/no_overlap_sample_sat.ipynb
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First, you must install ortools package in this colab.
%pip install ortools
Code sample to demonstrate how to build a NoOverlap constraint.
from ortools.sat.python import cp_model
def no_overlap_sample_sat():
"""No overlap sample with fixed activities."""
model = cp_model.CpModel()
horizon = 21 # 3 weeks.
# Task 0, duration 2.
start_0 = model.new_int_var(0, horizon, "start_0")
duration_0 = 2 # Python cp/sat code accepts integer variables or constants.
end_0 = model.new_int_var(0, horizon, "end_0")
task_0 = model.new_interval_var(start_0, duration_0, end_0, "task_0")
# Task 1, duration 4.
start_1 = model.new_int_var(0, horizon, "start_1")
duration_1 = 4 # Python cp/sat code accepts integer variables or constants.
end_1 = model.new_int_var(0, horizon, "end_1")
task_1 = model.new_interval_var(start_1, duration_1, end_1, "task_1")
# Task 2, duration 3.
start_2 = model.new_int_var(0, horizon, "start_2")
duration_2 = 3 # Python cp/sat code accepts integer variables or constants.
end_2 = model.new_int_var(0, horizon, "end_2")
task_2 = model.new_interval_var(start_2, duration_2, end_2, "task_2")
# Weekends.
weekend_0 = model.new_interval_var(5, 2, 7, "weekend_0")
weekend_1 = model.new_interval_var(12, 2, 14, "weekend_1")
weekend_2 = model.new_interval_var(19, 2, 21, "weekend_2")
# No Overlap constraint.
model.add_no_overlap([task_0, task_1, task_2, weekend_0, weekend_1, weekend_2])
# Makespan objective.
obj = model.new_int_var(0, horizon, "makespan")
model.add_max_equality(obj, [end_0, end_1, end_2])
model.minimize(obj)
# Solve model.
solver = cp_model.CpSolver()
status = solver.solve(model)
if status == cp_model.OPTIMAL:
# Print out makespan and the start times for all tasks.
print(f"Optimal Schedule Length: {solver.objective_value}")
print(f"Task 0 starts at {solver.value(start_0)}")
print(f"Task 1 starts at {solver.value(start_1)}")
print(f"Task 2 starts at {solver.value(start_2)}")
else:
print(f"Solver exited with nonoptimal status: {status}")
no_overlap_sample_sat()