分析 CPU 时间
您正在优化一个执行大量计算的金融分析应用。为准确了解处理器的使用情况，您需要实现一个工具，用于测量不同操作所消耗的精确 CPU 时间，帮助您识别哪些计算真正是 CPU 密集型。
所需的 lang.management 包已为您导入。
本练习是课程的一部分
Java 代码优化
练习说明
- 从
ManagementFactory类中获取ThreadMXBean实例。 - 获取当前线程的 CPU 时间。
交互式实操练习
通过完成这段示例代码来试试这个练习。
public class Main {
public static long getCpuTimeNano() {
// Retrieve the ThreadMXBean instance
ThreadMXBean threadMXBean = ____.____()
if (threadMXBean.isThreadCpuTimeSupported()) {
threadMXBean.setThreadCpuTimeEnabled(true);
// Return the current thread CPU time
return ____(Thread.currentThread().threadId());
} else {
System.out.println("CPU time measurement not supported");
return 0;
}
}
public static long calculateSum(long n) {
long sum = 0;
for (long i = 1; i <= n; i++) {
sum += i;
}
return sum;
}
public static long calculateSquareSum(long n) {
long sum = 0;
for (long i = 1; i <= n; i++) {
sum += i * i;
}
return sum;
}
public static void main(String[] args) {
long n = 100_000_000; // 100 million
long startSum = getCpuTimeNano();
long sum = calculateSum(n);
long endSum = getCpuTimeNano();
System.out.println("CPU time for sum: " +
((endSum - startSum) / 1_000_000.0) + " ms");
long startSquareSum = getCpuTimeNano();
long squareSum = calculateSquareSum(n);
long endSquareSum = getCpuTimeNano();
System.out.println("CPU time for square sum: " +
((endSquareSum - startSquareSum) / 1_000_000.0) + " ms");
double ratio = (endSquareSum - startSquareSum) / (double)(endSum - startSum);
System.out.println("Square sum takes " + ratio +
" times more CPU time than regular sum");
}
}