C++ in VSCode vs Python

Question

This is my problem, I've been trying to code in C++ in VSCode, so I followed the VSCode tutorial and installed Mingw-w64 via MSYS2 and everything works. But when I compile the file and execute the exe file in VSCode terminal, it's so slow, so I made a test speed with Python and Python wins. There has to be something wrong. This are my results.

import time
start = time.time()

for i in range(1000):
   for e in range(i):
       if (e*i)%2 == 0:
           print(e*i)

end = time.time()
print(end - start)

This is a random program to test the speed in Python and it takes 74 seconds in VSCode terminal and 16 seconds in the Command Prompt (I don't know why the VSCode terminal is that slow)

#include <iostream>
#include <chrono>

using namespace std::chrono;
using namespace std;

int main(){
   auto start = high_resolution_clock::now();
   for (int i=0; i<1000; i++){
      for (int e=0; e<i; e++){
         if ((e*i) % 2 == 0){
            cout<<e*i<<endl;
         }
      }
   }
   auto stop = high_resolution_clock::now();
   auto duration = duration_cast<microseconds>(stop - start);
   cout << duration.count() << endl;
}

This is the same program written in C++, which would have to be faster, but when I compile it and execute the exe file, it takes over 2 minutes to run in VSCode terminal and 60 seconds in the Command Prompt. Where is the problem? In the compiler? In VSCode? Why is the program faster in the Command Prompt and Why is Python faster?

Did you turn on the optimizer? If not, you're building debug code and that's easy to debug, but notoriously inefficient. — user4581301, Aug 11 '21 at 21:45
Edit your tasks.json and add `-O3` to your args. You also may want to replace `cout< — drescherjm, Aug 11 '21 at 21:49
A quick note on using `high_resolution_clock` from one of the people most responsible for creating it: [What are the uses of std::chrono::high_resolution_clock?](https://stackoverflow.com/a/37440647/4581301) — user4581301, Aug 11 '21 at 21:54
Might explain a bit: [C++ outputs differently than Python by default](https://stackoverflow.com/questions/66406245/why-my-c-program-is-100x-slower-than-a-python-version/66406471#66406471) — Anon Coward, Aug 11 '21 at 22:45

score 2 · Accepted Answer · answered Aug 11 '21 at 21:49

This is not about the program itself. This is all about how IDE and command prompt handle such a huge amount of output strings.

Of course, some difference between C++ streams vs python exists, as well. C++ streams do much more work on strings.

Anyway, the key problem is the amount of strings to be printed.

You may try: you_file.exe > results.txt and you will see more real performance.

Another way is to make the output to the file or output less strings.

Also, make sure that you are not in Debug mode in one of your cases.

Thanks, the problem was the huge amount of outputs, now C++ performs so much faster than Python — Tito Diego, Aug 11 '21 at 22:05

C++ in VSCode vs Python

1 Answers1