143 lines
4.9 KiB
Python
143 lines
4.9 KiB
Python
# Copyright 2010-2021 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Solves a simple shift scheduling problem."""
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from ortools.sat.python import cp_model
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class SolutionPrinter(cp_model.CpSolverSolutionCallback):
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"""Print intermediate solutions."""
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def __init__(self, num_vendors, num_hours, possible_schedules,
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selected_schedules, hours_stat, min_vendors):
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cp_model.CpSolverSolutionCallback.__init__(self)
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self.__solution_count = 0
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self.__num_vendors = num_vendors
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self.__num_hours = num_hours
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self.__possible_schedules = possible_schedules
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self.__selected_schedules = selected_schedules
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self.__hours_stat = hours_stat
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self.__min_vendors = min_vendors
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def on_solution_callback(self):
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"""Called at each new solution."""
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self.__solution_count += 1
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print('Solution %i: ', self.__solution_count)
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print(' min vendors:', self.__min_vendors)
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for i in range(self.__num_vendors):
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print(' - vendor %i: ' % i, self.__possible_schedules[self.Value(
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self.__selected_schedules[i])])
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print()
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for j in range(self.__num_hours):
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print(' - # workers on day%2i: ' % j, end=' ')
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print(self.Value(self.__hours_stat[j]), end=' ')
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print()
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print()
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def solution_count(self):
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"""Returns the number of solution found."""
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return self.__solution_count
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def main():
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"""Create the shift scheduling model and solve it."""
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# Create the model.
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model = cp_model.CpModel()
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#
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# data
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#
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num_vendors = 9
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num_hours = 10
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num_work_types = 1
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traffic = [100, 500, 100, 200, 320, 300, 200, 220, 300, 120]
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max_traffic_per_vendor = 100
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# Last columns are :
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# index_of_the_schedule, sum of worked hours (per work type).
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# The index is useful for branching.
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possible_schedules = [[1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0,
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8], [1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1,
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4], [0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 2,
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5], [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 3, 4],
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[1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 4,
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3], [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0]]
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num_possible_schedules = len(possible_schedules)
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selected_schedules = []
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vendors_stat = []
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hours_stat = []
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# Auxiliary data
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min_vendors = [t // max_traffic_per_vendor for t in traffic]
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all_vendors = range(num_vendors)
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all_hours = range(num_hours)
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#
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# declare variables
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#
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x = {}
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for v in all_vendors:
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tmp = []
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for h in all_hours:
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x[v, h] = model.NewIntVar(0, num_work_types, 'x[%i,%i]' % (v, h))
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tmp.append(x[v, h])
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selected_schedule = model.NewIntVar(0, num_possible_schedules - 1,
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's[%i]' % v)
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hours = model.NewIntVar(0, num_hours, 'h[%i]' % v)
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selected_schedules.append(selected_schedule)
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vendors_stat.append(hours)
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tmp.append(selected_schedule)
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tmp.append(hours)
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model.AddAllowedAssignments(tmp, possible_schedules)
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#
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# Statistics and constraints for each hour
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#
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for h in all_hours:
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workers = model.NewIntVar(0, 1000, 'workers[%i]' % h)
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model.Add(workers == sum(x[v, h] for v in all_vendors))
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hours_stat.append(workers)
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model.Add(workers * max_traffic_per_vendor >= traffic[h])
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#
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# Redundant constraint: sort selected_schedules
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#
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for v in range(num_vendors - 1):
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model.Add(selected_schedules[v] <= selected_schedules[v + 1])
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# Solve model.
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solver = cp_model.CpSolver()
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solver.parameters.enumerate_all_solutions = True
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solution_printer = SolutionPrinter(num_vendors, num_hours,
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possible_schedules, selected_schedules,
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hours_stat, min_vendors)
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status = solver.Solve(model, solution_printer)
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print('Status = %s' % solver.StatusName(status))
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print('Statistics')
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print(' - conflicts : %i' % solver.NumConflicts())
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print(' - branches : %i' % solver.NumBranches())
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print(' - wall time : %f s' % solver.WallTime())
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print(
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' - number of solutions found: %i' % solution_printer.solution_count())
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if __name__ == '__main__':
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main()
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