编写一个程序,使用多线程计算从1到N的所有数字的平方和,其中N为用户输入的正整数。使用多线程来加速计算过程。
要求:
(1)使用 C++的线程库 (std::thread)实现多线程。
2)程序应该能够处理较大的N值,确保计算结果的准确性和效率。“程序应具有良好的线程同步和数据共享机制,以避免竞争条件和数据不致的问题
#include <iostream>
#include <thread>
#include <vector>
#include <mutex>
std::mutex mtx;
long long sum = 0;
void square_sum(int start, int end) {
long long partial_sum = 0;
for (int i = start; i <= end; i++) {
partial_sum += i * i;
}
std::unique_lock<std::mutex> lock(mtx);
sum += partial_sum;
}
int main() {
int N;
std::cout << "Enter a positive integer: ";
std::cin >> N;
int num_threads = std::thread::hardware_concurrency();
std::vector<std::thread> threads(num_threads);
int chunk_size = N / num_threads;
for (int i = 0; i < num_threads; i++) {
int start = i * chunk_size + 1;
int end = (i == num_threads - 1) ? N : (i + 1) * chunk_size;
threads[i] = std::thread(square_sum, start, end);
}
for (auto& t : threads) {
t.join();
}
std::cout << "The sum of squares from 1 to " << N << " is " << sum << std::endl;
return 0;
}