c++ vector 并发

C++中的vector可以通过并发来提高程序的性能。下面是两种实现并发的方式：

1. 单线程版：

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
using namespace std;

int GetSum(vector<int>::iterator first, vector<int>::iterator last) {
    return accumulate(first, last, 0); // 调用C++标准库算法
}

int main() {
    vector<int> largeArrays;
    for (int i = 0; i < 100000000; i++) {
        if (i % 2 == 0)
            largeArrays.push_back(i);
        else
            largeArrays.push_back(-1 * i);
    }

    int res = GetSum(largeArrays.begin(), largeArrays.end());
    return 0;
}

2. 多线程版：

#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <thread>
using namespace std;

int GetSum(vector<int>::iterator first, vector<int>::iterator last) {
    return accumulate(first, last, 0); // 调用C++标准库算法
}

int main() {
    vector<int> largeArrays;
    for (int i = 0; i < 100000000; i++) {
        if (i % 2 == 0)
            largeArrays.push_back(i);
        else
            largeArrays.push_back(-1 * i);
    }

    int numThreads = 5;
    vector<thread> threads;
    int chunkSize = largeArrays.size() / numThreads;
    auto first = largeArrays.begin();
    auto last = first + chunkSize;

    for (int i = 0; i < numThreads; i++) {
        threads.push_back(thread(GetSum, first, last));
        first = last;
        last += chunkSize;
    }

    int res = 0;
    for (auto& t : threads) {
        t.join();
        res += GetSum(first, last);
    }

    return 0;
}