q1.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>

const int CW_TIME = 10000000;

// Threaded task
void *childsWork(void *param) {
    int *args = (int*)param;
    int ID = args[0];

    // Simulate the random length of time a process could take
    int length = rand() % CW_TIME;
    int l = length;
    while (--l > 0);

    printf("{ Child: %d, Thread ID: %u, Task length: %d }\n", ID, pthread_self(), length);
}

int main(int argc, char **argv) {
    int err;
    srand(time(NULL));

    // Get stdin
    int numThreads;
    char c;
    if (err = sscanf(argv[1], "%d %c", &numThreads, &c) != 1) {
        printf("Failed to provide integer argument, err code %d\n", err);
        return -1;
    }

    // Run threads
    int i;
    pthread_t *thread_id = (pthread_t *)malloc(numThreads * sizeof(pthread_t));
    int *index = (int *)malloc(numThreads * sizeof(int));

    for (i = 0; i < numThreads; i++) {
        index[i] = i;
        if (err = (pthread_create(&thread_id[i], NULL, childsWork, &index[i]) == 1)) {
            printf("Error creating thread, err code: %d\n", err);
            return -1;
        }
    }
    for (i = 0; i < numThreads; i++) {
        if (err = pthread_join(thread_id[i], NULL) == 1) {
            printf("Error joining thread, err code: %d\n", err);
            return -1;
        }
    }

    free(thread_id);
    free(index);
    return 0;
}

q2.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>

pthread_barrier_t barrier;

// Threaded task
void *childsWork(void *param) {
    int *args = (int*)param;
    int ID = args[0];

    printf("p1 -- { Child: %d, TID: %u }\n", ID, pthread_self());
    pthread_barrier_wait(&barrier);
    printf("{ Child: %d, TID: %u } -- 2\n", ID, pthread_self());
}

int main(int argc, char **argv) {
    int err;

    // Get stdin
    int numThreads;
    char c;
    if (err = sscanf(argv[1], "%d %c", &numThreads, &c) != 1) {
        printf("Failed to provide integer argument, err code: %d\n", err);
        return -1;
    }
    pthread_barrier_init(&barrier, NULL, numThreads);


    // Run threads
    int i;
    pthread_t *thread_id = (pthread_t *)malloc(numThreads *sizeof(pthread_t));
    int *index = (int *)malloc(numThreads * sizeof(int));

    for (i = 0; i < numThreads; i++) {
        index[i] = i;
        if (err = pthread_create(&thread_id[i], NULL, childsWork, &index[i]) == 1) {
            printf("Error creating thread, err code: %d\n", err);
            return -1;
        }
    }
    for (i = 0; i < numThreads; i++) {
        if (err = pthread_join(thread_id[i], NULL) == 1) {
            printf("Error joining thread, err code: %d\n", err);
            return -1;
        }
    }

    pthread_barrier_destroy(&barrier);
    free(thread_id);
    free(index);
    return 0;
}

q3.c

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>

pthread_barrier_t barrier;
int A[] = {1, 1};

// Threaded task 1
void *backend(void *unused) {
    for (int i = 0; i < 10; i++) {
        pthread_barrier_wait(&barrier);
        pthread_barrier_wait(&barrier);

        // Calculate the next two numbers of the fibonacci sequence
        int x = A[0] + A[1], y = A[1] + x;;
        A[0] = x;
        A[1] = y;
    }
}

// Threaded task 2
void *frontend(void *unused) {
    for (int i = 0; i < 10; i++) {
        pthread_barrier_wait(&barrier);

        printf("{ %d, %d }\n", A[0], A[1]);

        pthread_barrier_wait(&barrier);
    }
}

int main(int argc, char **argv) {
    int err;
    pthread_barrier_init(&barrier, NULL, 2);

    // Run threads
    pthread_t *backend_tid = (pthread_t *) malloc(sizeof(pthread_t));
    pthread_t *frontend_tid = (pthread_t *) malloc(sizeof(pthread_t));
    int null;

    if ( err = pthread_create(backend_tid, NULL, backend, &null) == 1) {
        printf("Error creating thread, err code: %d\n", err);
        return -1;
    }
    if ( err = pthread_create(frontend_tid, NULL, frontend, &null) == 1) {
        printf("Error creating thread, err code: %d\n", err);
        return -1;
    }

    if (err = pthread_join(*backend_tid, NULL) == 1) {
        printf("Error joining thread, err code: %d %s\n", err);
        return -1;
    }
    if (err = pthread_join(*frontend_tid, NULL) == 1) {
        printf("Error joining thread, err code: %d\n", err);
        return -1;
    }

    pthread_barrier_destroy(&barrier);
    free(backend_tid);
    free(frontend_tid);
    return 0;
}