Program containing threading in cpp is not executed completely

Question

Code given below is not executed completely;
I have looked for everything on web but I don't know why it is working for starting numbers from nums (i.e. 1000 and sometimes 5000) and after that it starts execution but in between program terminates itself and stopes working.

#include <bits/stdc++.h>
// #include <iostream>
// #include <chrono>
// #include <vector>

#define UPPER_LIMIT 10

using namespace std;
using namespace std::chrono;

bool inTimeLimit = true;
bool isFinished = false;
bool isRunning = true;

class Timer {
public:
    time_point<high_resolution_clock> start, end;

    Timer() {
        start = high_resolution_clock::now();
    }

    ~Timer() {
        end = high_resolution_clock::now();
        auto durationTime = durationCounter();

        cout << "\n\nTaken time Duration " << (unsigned long long)durationTime << " us; " << (unsigned long long)durationTime * 0.001  << "ms.";
    }

    float durationCounter() {
        auto currTime = high_resolution_clock::now();
        auto durationTime = duration_cast<microseconds>(currTime - start);

        return durationTime.count();
    }
};


void printVector(vector <int> v) {
    cout << endl;
    for (int x : v) {
        cout << setw(3) << x << " ";
    }
}

void printVectorToFile(ofstream &fout , vector <int> v, string msg) {


    fout << "\n\n===================\n\n";
    fout << msg << endl;
    fout << endl;
    for (int x : v) {
        fout << setw(5) << x << " ";
    }
    fout << endl;
}

void swap (int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

vector <int> randomArrayGenerator(int n) {

    vector<int> v(n);
    for (int i = 0; i < n; ++i)
        v[i] = i + 1;

    srand(time(0));
    for (int i = 0; i < n; ++i)
    {
        int pos = rand() % n;
        swap(&v[i], &v[pos]);
    }

    return v;
}

string sortingChecker(vector<int> v) {
    for (int i = 0; i < (int)v.size() - 1; ++i)
    {
        if (v[i] > v[i + 1])    return "false";
    }
    return "true";
}

bool sortChecker(vector<int> v) {
    for (int i = 0; i < (int)v.size() - 1; ++i)
    {
        if (v[i] > v[i + 1])    return false;
    }
    return true;
}


// Merge function

void merge(vector <int> &v, int begin, int middle, int end) {
    vector <int> left, right;

    for (int i = begin; i < middle + 1; ++i)
    {
        left.push_back(v[i]);
    }
    for (int i = middle + 1; i <= end; ++i)
    {
        right.push_back(v[i]);
    }


    int p1 = 0, p2 = 0, n1 = left.size(), n2 = right.size(), p = begin;
    while ((p1 < n1 ) || (p2 < n2)) {
        if ((p1 != n1 ) && ((p2 == n2) || left[p1] < right[p2]))
            v[p++] = left[p1++];
        else
            v[p++] = right[p2++];
    }

}


void mergeSortByIteration(vector <int> &v, bool &isTimeDelayed) {

    int low = 0, high = v.size();
    cout << "Thread ID: " << this_thread::get_id() << endl;
    // n :for taking individual block of vector containing number of elements n=[1,2,4,8,..]
    for (int n = 1; n < high; n *= 2) {
        if (isTimeDelayed) return;
        // taking block according to n and then sorting them by merge function
        // n=1 => i=0,2,4,8,16
        // n=2 => i=0,4,8
        for (int i = 0; i < high; i += 2 * n) {
            if (isTimeDelayed) return;
            int begin = i;
            int mid =  i + n - 1;
            int end = min(i + 2 * n - 1 , high - 1);

            merge(v, begin, mid, end);
        }

    }

}

// Merge by recurision

void mergeSortByRecursion (vector <int> &v, int begin, int end, bool &isTimeDelayed) {
    if (end <= begin || isTimeDelayed) return;
    int middle = begin + (end - begin) / 2;
    mergeSortByRecursion(v, begin, middle, isTimeDelayed);
    mergeSortByRecursion(v, middle + 1, end, isTimeDelayed);
    merge(v, begin, middle, end);

}


int main() {

    int nums[] = {1000, 5000, 10000, 50000, 100000};

    // int nums[] = {50000};
    ofstream vectorOutput ;
    vectorOutput.open("outputTexts\\prac1_resultedArrays.txt", ios::trunc);;
    for (int n : nums)
// ``````` Merge by Iteration ````````
    {
        vector<int> num, arr = randomArrayGenerator(n);
        cout << "\n=======";
        cout << "\n\nMerge by Iteration:" << endl;
        num = arr;


        cout << "Array size: " << num.size() << endl;

        bool isTimeOut = false, isSorted = false;
        Timer timer;

        std::thread worker(mergeSortByIteration, ref(num), ref(isTimeOut));

        // mergeSortByIteration(num, isTimeOut);

        // std::thread worker(mergeSortByRecursion, ref(num), 0, n - 1, ref(isTimeOut));


        while ( ( ( timer.durationCounter() / 1000000 ) < 5) && (!isSorted ) ) {
            // this_thread::sleep_for(seconds(1));
            // cout  << timer.durationCounter()  << " ";
            isSorted = sortChecker(num);
        }

        if ( ( ( ( timer.durationCounter() / 1000000 ) > 5) && (!isSorted ) ) )
        {
            isTimeOut = true;
            cout << endl << "!!!!!Execution Terminated ---- Time Limit reached!!!!!!" << endl;
        }

        if (worker.joinable())
            worker.join();

        printVector(num);

        cout << "\nCheck result for sorted Vector:" << (isSorted ? "true" : "false") << endl;

        // printVectorToFile(vectorOutput, num, "Merge By Iteration for size:" + to_string(n) );

    }

    cout << "\n\ndone" << endl;

    return 0;
}

can anyone help me out here? If issue is not clear fill free to ask.