C++17並行STL

嘗試了一下C++17的並行STL排序，速度提升比較明顯。

環境是VS2019。

#include <algorithm>
#include <execution>
#include <iostream>
#include <random>
#include <chrono>   

using namespace std;
using namespace chrono;

int main() 
{
    vector<long long> d1(30000000);
    vector<long long> d2(30000000);

    mt19937 gen;
    uniform_int_distribution<long long> dis(0, 100000000);
    auto rand_num([=]() mutable { return dis(gen); });

    generate(execution::par, begin(d1), end(d1), rand_num);
    d2 = d1;
    
    auto start_t = high_resolution_clock::now();
    sort(begin(d1), end(d1));
    auto end_t = high_resolution_clock::now();
    auto duration = duration_cast<nanoseconds>(end_t - start_t);
    cout << "The run time is: " << double(duration.count()) * nanoseconds::period::num / nanoseconds::period::den << "s" << endl;

    start_t = high_resolution_clock::now();
    sort(execution::par, begin(d2), end(d2));
    end_t = high_resolution_clock::now();
    duration = duration_cast<nanoseconds>(end_t - start_t);
    cout << "The run time is: " << double(duration.count()) * nanoseconds::period::num / nanoseconds::period::den << "s" << endl;
   
    return 0;
}

速度對比：