117 lines
3.5 KiB
Java
117 lines
3.5 KiB
Java
// Copyright 2010-2018 Google LLC
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
// CP-SAT example that solves an assignment problem.
|
|
// [START program]
|
|
package com.google.ortools.sat.samples;
|
|
// [START import]
|
|
import com.google.ortools.Loader;
|
|
import com.google.ortools.sat.CpModel;
|
|
import com.google.ortools.sat.CpSolver;
|
|
import com.google.ortools.sat.CpSolverStatus;
|
|
import com.google.ortools.sat.IntVar;
|
|
import com.google.ortools.sat.LinearExpr;
|
|
// [END import]
|
|
|
|
/** Assignment problem. */
|
|
public class AssignmentSat {
|
|
public static void main(String[] args) {
|
|
Loader.loadNativeLibraries();
|
|
// Data
|
|
// [START data_model]
|
|
int[][] costs = {
|
|
{90, 80, 75, 70},
|
|
{35, 85, 55, 65},
|
|
{125, 95, 90, 95},
|
|
{45, 110, 95, 115},
|
|
{50, 100, 90, 100},
|
|
};
|
|
final int numWorkers = costs.length;
|
|
final int numTasks = costs[0].length;
|
|
// [END data_model]
|
|
|
|
// Model
|
|
// [START model]
|
|
CpModel model = new CpModel();
|
|
// [END model]
|
|
|
|
// Variables
|
|
// [START variables]
|
|
IntVar[][] x = new IntVar[numWorkers][numTasks];
|
|
// Variables in a 1-dim array.
|
|
IntVar[] xFlat = new IntVar[numWorkers * numTasks];
|
|
int[] costsFlat = new int[numWorkers * numTasks];
|
|
for (int i = 0; i < numWorkers; ++i) {
|
|
for (int j = 0; j < numTasks; ++j) {
|
|
x[i][j] = model.newIntVar(0, 1, "");
|
|
int k = i * numTasks + j;
|
|
xFlat[k] = x[i][j];
|
|
costsFlat[k] = costs[i][j];
|
|
}
|
|
}
|
|
// [END variables]
|
|
|
|
// Constraints
|
|
// [START constraints]
|
|
// Each worker is assigned to at most one task.
|
|
for (int i = 0; i < numWorkers; ++i) {
|
|
IntVar[] vars = new IntVar[numTasks];
|
|
for (int j = 0; j < numTasks; ++j) {
|
|
vars[j] = x[i][j];
|
|
}
|
|
model.addLessOrEqual(LinearExpr.sum(vars), 1);
|
|
}
|
|
// Each task is assigned to exactly one worker.
|
|
for (int j = 0; j < numTasks; ++j) {
|
|
// LinearExpr taskSum;
|
|
IntVar[] vars = new IntVar[numWorkers];
|
|
for (int i = 0; i < numWorkers; ++i) {
|
|
vars[i] = x[i][j];
|
|
}
|
|
model.addEquality(LinearExpr.sum(vars), 1);
|
|
}
|
|
// [END constraints]
|
|
|
|
// Objective
|
|
// [START objective]
|
|
model.minimize(LinearExpr.scalProd(xFlat, costsFlat));
|
|
// [END objective]
|
|
|
|
// Solve
|
|
// [START solve]
|
|
CpSolver solver = new CpSolver();
|
|
CpSolverStatus status = solver.solve(model);
|
|
// [END solve]
|
|
|
|
// Print solution.
|
|
// [START print_solution]
|
|
// Check that the problem has a feasible solution.
|
|
if (status == CpSolverStatus.OPTIMAL || status == CpSolverStatus.FEASIBLE) {
|
|
System.out.println("Total cost: " + solver.objectiveValue() + "\n");
|
|
for (int i = 0; i < numWorkers; ++i) {
|
|
for (int j = 0; j < numTasks; ++j) {
|
|
if (solver.value(x[i][j]) == 1) {
|
|
System.out.println(
|
|
"Worker " + i + " assigned to task " + j + ". Cost: " + costs[i][j]);
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
System.err.println("No solution found.");
|
|
}
|
|
// [END print_solution]
|
|
}
|
|
|
|
private AssignmentSat() {}
|
|
}
|