写出Java调用cplex的具体代码,解决刚刚的问题
时间: 2024-02-17 16:00:18 浏览: 75
CPLEX Tutorial Handout
好的,以下是一个简单的Java调用CPLEX求解VRP问题的示例代码:
```java
import ilog.concert.*;
import ilog.cplex.*;
public class VRP {
public static void main(String[] args) {
try {
// 创建 CPLEX 模型对象
IloCplex cplex = new IloCplex();
// 创建变量 x[i][j][k],表示从客户 i 到客户 j 用车 k 进行配送的数量
int numCustomers = 10;
int numVehicles = 3;
IloIntVar[][][] x = new IloIntVar[numCustomers+1][numCustomers+1][numVehicles+1];
for (int i = 1; i <= numCustomers; i++) {
for (int j = 1; j <= numCustomers; j++) {
for (int k = 1; k <= numVehicles; k++) {
x[i][j][k] = cplex.intVar(0, Integer.MAX_VALUE);
}
}
}
// 创建变量 y[j][k],表示车 k 是否会访问客户 j
IloIntVar[][] y = new IloIntVar[numCustomers+1][numVehicles+1];
for (int j = 1; j <= numCustomers; j++) {
for (int k = 1; k <= numVehicles; k++) {
y[j][k] = cplex.boolVar();
}
}
// 创建目标函数,最小化配送成本
IloLinearNumExpr costExpr = cplex.linearNumExpr();
for (int i = 1; i <= numCustomers; i++) {
for (int j = 1; j <= numCustomers; j++) {
for (int k = 1; k <= numVehicles; k++) {
costExpr.addTerm(distance(i, j), x[i][j][k]);
}
}
}
cplex.addMinimize(costExpr);
// 添加约束条件,每个客户必须被访问一次
for (int j = 1; j <= numCustomers; j++) {
IloLinearNumExpr visitExpr = cplex.linearNumExpr();
for (int i = 1; i <= numCustomers; i++) {
for (int k = 1; k <= numVehicles; k++) {
visitExpr.addTerm(1, x[i][j][k]);
}
}
cplex.addEq(visitExpr, 1);
}
// 添加约束条件,每辆车的容量不能超过限制
int[] demand = {10, 20, 30, 10, 5, 15, 5, 10, 10, 5};
int capacity = 50;
for (int k = 1; k <= numVehicles; k++) {
IloLinearNumExpr capacityExpr = cplex.linearNumExpr();
for (int j = 1; j <= numCustomers; j++) {
capacityExpr.addTerm(demand[j-1], y[j][k]);
for (int i = 1; i <= numCustomers; i++) {
capacityExpr.addTerm(-demand[j-1], x[i][j][k]);
}
}
cplex.addLe(capacityExpr, capacity);
}
// 添加约束条件,车辆必须从总部出发并返回
for (int k = 1; k <= numVehicles; k++) {
IloLinearNumExpr originExpr = cplex.linearNumExpr();
for (int j = 1; j <= numCustomers; j++) {
originExpr.addTerm(1, y[j][k]);
originExpr.addTerm(-1, y[0][k]);
}
cplex.addEq(originExpr, 0);
}
// 求解模型
if (cplex.solve()) {
// 输出结果
System.out.println("Total cost: " + cplex.getObjValue());
for (int i = 1; i <= numCustomers; i++) {
for (int j = 1; j <= numCustomers; j++) {
for (int k = 1; k <= numVehicles; k++) {
if (cplex.getValue(x[i][j][k]) > 0.0001) {
System.out.println("Vehicle " + k + " delivers " + cplex.getValue(x[i][j][k]) + " units from customer " + i + " to customer " + j);
}
}
}
}
} else {
System.out.println("No solution found.");
}
// 释放 CPLEX 资源
cplex.end();
} catch (IloException e) {
System.err.println("Concert exception caught: " + e);
}
}
// 计算客户 i 和客户 j 之间的距离
private static double distance(int i, int j) {
int[][] coordinates = {{0, 0}, {40, 50}, {45, 68}, {60, 70}, {70, 40}, {66, 20}, {30, 25}, {20, 30}, {15, 45}, {45, 35}, {35, 20}};
int dx = coordinates[i][0] - coordinates[j][0];
int dy = coordinates[i][1] - coordinates[j][1];
return Math.sqrt(dx*dx + dy*dy);
}
}
```
这个示例程序使用CPLEX求解VRP问题,并输出了每辆车的配送方案以及总成本。在这个示例中,您需要将CPLEX的Java API添加到您的项目依赖中,并按照示例中的方式创建模型、变量和约束条件。然后,您可以调用`cplex.solve()`方法来求解模型,并使用`cplex.getValue()`方法获取每个变量的值。
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