I am using threading in c++, on MAC for the first time.

Below is my code. (Motivation behind my code)

#include <iostream>
#include <thread>
#include <chrono>

using namespace std;

using namespace chrono;

const long long maxLimit = 2e9;

void getEvenSum(long long &sum) {
    for(int i = 0 ; i <= maxLimit ; i+=2) {
        sum += i;
    }
}

void getOddSum(long long &sum) {
    for(int i = 1 ; i <= maxLimit ; i+=2) {
        sum += i;
    }
}

int main() {
    
    auto startTime = high_resolution_clock::now();
    
    long long evenSum = 0 , oddSum = 0;
    thread evenSumThread(getEvenSum, ref(evenSum));
    thread oddSumThread(getOddSum, ref(oddSum));

    evenSumThread.join();
    oddSumThread.join();

    auto endTime = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(endTime - startTime);

    cout << " final sum is " << evenSum << " " << oddSum << endl;

    cout << " time taken with thread :" << duration.count() / (long double)1e6 << endl;

    

    startTime = high_resolution_clock::now();
    
    evenSum = 0 , oddSum = 0;
    getEvenSum(evenSum);
    getOddSum(oddSum);

    endTime = high_resolution_clock::now();
    duration = duration_cast<microseconds>(endTime - startTime);

    cout << " final sum is " << evenSum << " " << oddSum << endl;

    cout << " time taken without thread " << duration.count() / (long double)1e6 << endl;

    return 0;

}

OUTPUT :

 final sum is 1000000001000000000 1000000000000000000
 time taken with thread :5.01665
 final sum is 1000000001000000000 1000000000000000000
 time taken without thread 2.83442

The output is quite unexpected. Threading takes 5 seconds and non-threading takes 2.8 seconds. HOW !!!

Solutions I have tried and failed,

1. g++ --std=c++11 file.cpp
2. g++ --std=c++11 -O3 -s -DNDEBUG file.cpp ( time changed frantically, but still threading takes more time )
3. g++ --std=c++17 file.cpp
4. g++ clang++ -std=c++11 file.cpp ( Got error, that “CLANG” not present )
5. Tried changing XCode->Product->Scheme->Change Scheme ( Doesn’t open any menu for changing scheme, Dead end )
6. Above commands I have tried in VS code, as well as MAC terminal (iterm). I tried changing VS code build from “DEBUG” to “RELEASE”, that also doesn’t help.

PS : The same code used to work when I had practiced last time in the Linux (2 years back)