Multithreading calculates the sum of the squares of all numbers from 1 to N, where N is a positive integer entered by the user. Use multi-threading to speed up the computing process.

Write a program that uses multiple threads to calculate the sum of the squares of all numbers from 1 to N, where N is a positive integer entered by the user. Use multi-threading to speed up the computing process.

Require:

(1) Use the C++ thread library (std::thread) to implement multi-threading.

2) The program should be able to handle larger N values ​​to ensure the accuracy and efficiency of calculation results. "Programs should have good thread synchronization and data sharing mechanisms to avoid race conditions and data inconsistency problems

#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;
}