135 lines
4.1 KiB
Python
135 lines
4.1 KiB
Python
# Copyright 2010-2017 Google
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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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from __future__ import print_function
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from ortools.constraint_solver import pywrapcp
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def main():
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# Instantiate a cp solver.
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solver = pywrapcp.Solver('transportation_with_sizes')
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cost = [[90, 76, 75, 70, 50, 74], [35, 85, 55, 65, 48, 101],
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[125, 95, 90, 105, 59, 120], [45, 110, 95, 115, 104, 83],
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[60, 105, 80, 75, 59, 62], [45, 65, 110, 95, 47, 31],
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[38, 51, 107, 41, 69, 99], [47, 85, 57, 71, 92, 77],
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[39, 63, 97, 49, 118, 56], [47, 101, 71, 60, 88, 109],
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[17, 39, 103, 64, 61, 92], [101, 45, 83, 59, 92, 27]]
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group1 = [
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[0, 0, 1, 1], # Workers 2, 3
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[0, 1, 0, 1], # Workers 1, 3
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[0, 1, 1, 0], # Workers 1, 2
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[1, 1, 0, 0], # Workers 0, 1
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[1, 0, 1, 0]
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] # Workers 0, 2
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group2 = [
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[0, 0, 1, 1], # Workers 6, 7
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[0, 1, 0, 1], # Workers 5, 7
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[0, 1, 1, 0], # Workers 5, 6
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[1, 1, 0, 0], # Workers 4, 5
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[1, 0, 0, 1]
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] # Workers 4, 7
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group3 = [
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[0, 0, 1, 1], # Workers 10, 11
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[0, 1, 0, 1], # Workers 9, 11
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[0, 1, 1, 0], # Workers 9, 10
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[1, 0, 1, 0], # Workers 8, 10
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[1, 0, 0, 1]
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] # Workers 8, 11
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sizes = [10, 7, 3, 12, 15, 4, 11, 5]
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total_size_max = 15
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num_workers = len(cost)
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num_tasks = len(cost[1])
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# Variables
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total_cost = solver.IntVar(0, 1000, 'total_cost')
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x = []
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works = []
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for i in range(num_workers):
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work = solver.BoolVar('work[%i]' % i)
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works.append(work)
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t = []
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for j in range(num_tasks):
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t.append(solver.IntVar(0, 1, 'x[%i,%i]' % (i, j)))
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x.append(t)
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solver.Add(solver.MaxEquality(x[i], work))
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x_array = [x[i][j] for i in range(num_workers) for j in range(num_tasks)]
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# Constraints
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# Each task is assigned to at least one worker.
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[
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solver.Add(solver.Sum(x[i][j]
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for i in range(num_workers)) >= 1)
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for j in range(num_tasks)
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]
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# Total task size for each worker is at most total_size_max
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[
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solver.Add(
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solver.Sum(sizes[j] * x[i][j]
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for j in range(num_tasks)) <= total_size_max)
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for i in range(num_workers)
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]
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# Workers forms valid groups.
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solver.Add(
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solver.AllowedAssignments([works[0], works[1], works[2], works[3]],
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group1))
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solver.Add(
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solver.AllowedAssignments([works[4], works[5], works[6], works[7]],
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group2))
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solver.Add(
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solver.AllowedAssignments([works[8], works[9], works[10], works[11]],
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group3))
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# Total cost
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solver.Add(total_cost == solver.Sum(
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[solver.ScalProd(x_row, cost_row) for (x_row, cost_row) in zip(x, cost)]))
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objective = solver.Minimize(total_cost, 1)
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db = solver.Phase(x_array, solver.CHOOSE_FIRST_UNBOUND,
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solver.ASSIGN_MIN_VALUE)
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# Create a solution collector.
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collector = solver.LastSolutionCollector()
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# Add decision variables
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#collector.Add(x_array)
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for i in range(num_workers):
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collector.Add(x[i])
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# Add objective
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collector.AddObjective(total_cost)
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solver.Solve(db, [objective, collector])
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if collector.SolutionCount() > 0:
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best_solution = collector.SolutionCount() - 1
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print('Total cost = ', collector.ObjectiveValue(best_solution))
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print()
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for i in range(num_workers):
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for j in range(num_tasks):
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if collector.Value(best_solution, x[i][j]) == 1:
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print('Worker ', i, ' assigned to task ', j, ' Cost = ', cost[i][j])
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print()
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print('Time = ', solver.WallTime(), 'milliseconds')
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if __name__ == '__main__':
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main()
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