std::future And std::promise | Threading Cpp11

TOPIC: std::future and std::promise in threading.

NOTES:

1. std::promise

     a. Used to set values or exceptions.

2. std::future

     a. Used to get values from promise.

     b. Ask promise if the value is available.

     c. Wait for the promise.

PROGRAM:

#include <iostream>

#include <thread>

#include <chrono>

#include <algorithm>

#include <future>

using namespace std;

using namespace std::chrono;

typedef long int ull;

void findOdd(std::promise<ull>&& OddSumPromise, ull start, ull end) {

    ull OddSum = 0;

    for (ull i = start; i <= end; ++i){

        if (i & 1){

            OddSum += i;

        }

    }

    OddSumPromise.set_value(OddSum);

}

int main() {

    

    ull start = 0, end = 1900000000;

    std::promise<ull> OddSum;

    std::future<ull> OddFuture = OddSum.get_future();

    

    cout << "Thread Created!!" << endl;

    std::thread t1(findOdd, std::move(OddSum), start, end);

    

    cout << "Waiting For Result!!" << endl;

    cout << "OddSum : " << OddFuture.get() << endl;

    

    cout << "Completed!!" << endl;

    t1.join();

    return 0;

}