#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <assert.h>

#define VECTOR_COL 10000000
#define VECTOR_ROW 10

typedef struct {
    int* start;
    int* end;
    int count;
} IncrementArgs;

void* increment_subsection(void* increment_args)
{
    IncrementArgs* a = increment_args;

    for (; a->start < a->end; a->start++)
    {
        *(a->start) = a->count++;
    }

    return NULL;
}

int main (void)
{
    // Too big for stack, allocate elsewhere
    int* vector = (int*) calloc(VECTOR_COL * VECTOR_ROW, sizeof(int));
    int err = 0;
    IncrementArgs increment_args;
    IncrementArgs increment_args2;
    pthread_t set_lower_arr;
    pthread_t set_upper_arr;

    increment_args.start = vector;
    increment_args.end = vector+(VECTOR_COL/2)*VECTOR_ROW;
    increment_args.count = 0;
    err = pthread_create(&set_lower_arr, NULL, increment_subsection,
                       &increment_args);
    if (err)
    {
        printf("Error creating lower thread %d\n", err);
        return 1;
    }
    increment_args2.start = vector+(VECTOR_COL/2)*VECTOR_ROW;
    increment_args2.end = vector+(VECTOR_COL*VECTOR_ROW);
    increment_args2.count = VECTOR_COL*VECTOR_ROW / 2;
    err = pthread_create(&set_upper_arr, NULL, increment_subsection,
                       &increment_args2);
    if (err)
    {
        printf("Error creating upper thread %d\n", err);
        return 1;
    }

    if (pthread_join(set_upper_arr, NULL))
    {
        printf("Error joining thread\n");
        return 2;
    }

    if (pthread_join(set_lower_arr, NULL))
    {
        printf("Error joining thread\n");
        return 2;
    }

    free(vector);

    return 0;
}