87 lines
2.9 KiB
Java
87 lines
2.9 KiB
Java
/*
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* Copyright 2017 Darian Sastre darian.sastre@minimaxlabs.com
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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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*
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* ************************************************************************
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*
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* Each knapsack perceives a different weight for each item. Item values are
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* the same across knapsacks. Optimizing constrains the count of each item such
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* that all knapsack capacities are respected, and their values are maximized.
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*
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* This model was created by Hakan Kjellerstrand (hakank@gmail.com)
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*/
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package com.google.ortools.contrib;
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import com.google.ortools.Loader;
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import com.google.ortools.linearsolver.*;
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public class KnapsackMIP {
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private static void solve(String solverType) {
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MPSolver solver = MPSolver.createSolver(solverType);
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if (solver == null) {
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System.out.println("Could not create solver");
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return;
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}
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/** variables */
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int itemCount = 12;
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int capacityCount = 7;
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int[] capacity = {18209, 7692, 1333, 924, 26638, 61188, 13360};
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int[] value = {96, 76, 56, 11, 86, 10, 66, 86, 83, 12, 9, 81};
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int[][] weights = {{19, 1, 10, 1, 1, 14, 152, 11, 1, 1, 1, 1},
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{0, 4, 53, 0, 0, 80, 0, 4, 5, 0, 0, 0}, {4, 660, 3, 0, 30, 0, 3, 0, 4, 90, 0, 0},
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{7, 0, 18, 6, 770, 330, 7, 0, 0, 6, 0, 0}, {0, 20, 0, 4, 52, 3, 0, 0, 0, 5, 4, 0},
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{0, 0, 40, 70, 4, 63, 0, 0, 60, 0, 4, 0}, {0, 32, 0, 0, 0, 5, 0, 3, 0, 660, 0, 9}};
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int maxCapacity = -1;
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for (int c : capacity) {
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if (c > maxCapacity) {
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maxCapacity = c;
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}
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}
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MPVariable[] taken = solver.makeIntVarArray(itemCount, 0, maxCapacity);
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/** constraints */
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MPConstraint constraints[] = new MPConstraint[capacityCount];
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for (int i = 0; i < capacityCount; i++) {
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constraints[i] = solver.makeConstraint(0, capacity[i]);
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for (int j = 0; j < itemCount; j++) {
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constraints[i].setCoefficient(taken[j], weights[i][j]);
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}
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}
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/** objective */
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MPObjective obj = solver.objective();
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obj.setMaximization();
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for (int i = 0; i < itemCount; i++) {
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obj.setCoefficient(taken[i], value[i]);
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}
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solver.solve();
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/** printing */
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System.out.println("Max cost: " + obj.value());
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System.out.print("Item quantities: ");
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for (MPVariable var : taken) {
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System.out.print((int) var.solutionValue() + " ");
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}
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}
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public static void main(String[] args) {
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Loader.loadNativeLibraries();
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solve("CBC_MIXED_INTEGER_PROGRAMMING");
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}
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}
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