pthread v0.0.0.0.0.1

ahfkjahsdkfha.c

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

// debugging
#define HERE() printf("%s:%s:%d\n", __FILE__, __func__, __LINE__)

#define LENGTH 100000000
#define NUM_THREADS 2

// array with stored length
typedef struct {
  unsigned len;
  unsigned long long * data;
} len_array;

/* the function that's run in each thread */
void * sum(void* arg) {
  len_array * a = (len_array*)arg;
  unsigned len = a->len, i;

  unsigned long long * data = (unsigned long long*)a->data;
  unsigned long long acc = 0, cur;
  unsigned long long * ret;

  for (i = 0; i < len; i++) {
    cur = data[i];
    acc += cur;
  }

  ret = malloc(sizeof(unsigned long long));
  *ret = acc;

  return ret;
}

int main() {
  printf("Sum [1..%d] using %d thread%s\n", LENGTH, NUM_THREADS, NUM_THREADS == 1?"":"s");
  pthread_t threads[NUM_THREADS];

  unsigned long long * data = malloc(sizeof(unsigned long long) * LENGTH);
  len_array subdata[NUM_THREADS];

  unsigned i, avg_per_thread = LENGTH / NUM_THREADS, extra = LENGTH % NUM_THREADS, index = 0;

  for (i = 0; i < LENGTH; i++) {
    data[i] = (unsigned long long)i;
  }

  index = 0;
  for (i =0; i < NUM_THREADS; i++) {
    subdata[i].data = &(data[index]);
    subdata[i].len = avg_per_thread;
    index += avg_per_thread;
    if (extra > 0) {
      subdata[i].len++;
      extra--;
      index++;
    }

    pthread_create(&(threads[i]), NULL, sum, (void*)&(subdata[i]));
  }

  unsigned long long res = 0, * ret;
  for (i = 0; i < NUM_THREADS; i++) {
    pthread_join(threads[i], (void**)&ret);
    res += *(unsigned long long*)ret;
  }

  printf("%llu\n", res);
  return 0;
}