I saw in this cppcon that make_unique/make_shared are supposed to be faster but in the following program I ran in VSCode and compiled with g++ gives me different result.
#include <chrono>
#include <memory>
#include <iostream>
size_t len = 10000000;
int main(int argc, char const *argv[])
{
auto start = std::chrono::system_clock::now();
for (size_t i = 0; i < len; i++)
{
int* tmp(new int(i));
delete tmp;
}
std::chrono::duration<double> dur = std::chrono::system_clock::now() - start;
std::cout << "int* = " << dur.count() << "\n";
start = std::chrono::system_clock::now();
for (size_t i = 0; i < len; i++)
{
std::unique_ptr<int> tmp(new int(i));
}
dur = std::chrono::system_clock::now() - start;
std::cout << "std::unique_ptr = " << dur.count() << "\n";
start = std::chrono::system_clock::now();
for (size_t i = 0; i < len; i++)
{
std::unique_ptr<int> tmp = std::make_unique<int>(i);
}
dur = std::chrono::system_clock::now() - start;
std::cout << "std::make_unique = " << dur.count() << "\n";
start = std::chrono::system_clock::now();
for (size_t i = 0; i < len; i++)
{
std::shared_ptr<int> tmp(new int(i));
}
dur = std::chrono::system_clock::now() - start;
std::cout << "std::shared_ptr = " << dur.count() << "\n";
start = std::chrono::system_clock::now();
for (size_t i = 0; i < len; i++)
{
std::shared_ptr<int> tmp = std::make_shared<int>(i);
}
dur = std::chrono::system_clock::now() - start;
std::cout << "std::make_shared = " << dur.count() << "\n";
return 0;
}
Result:
int* = 0.709534
std::unique_ptr = 1.12149
std::make_unique = 1.14068
std::shared_ptr = 1.7354
std::make_shared = 2.13896
Can anyone please explain the mystery behind?
