memory management - How to declare and use huge arrays of 1 billion integers in C?

Question

I'm implementing a sequential program for sorting like quicksort. I would like to test the performance of my program in a huge array of 1 or 10 billions of integers. But the problem is that I obtain a segmentation error due to the size of the array.

A sample code of declaration of this array:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 1000000000

int main(int argc, char **argv)
{
  int list[N], i;
  srand(time(NULL));
  for(i=0; i<N; i++)
     list[i] = rand()%1000;
  return 0;
}

I got a proposition to use mmap function. But I don't know how to use it ? can anybody help me to use it ?

I'm working on Ubuntu 10.04 64-bit, gcc version 4.4.3.

Thanks for your replies.

Answer 1

You must use malloc for this sort of allocation. That much on the stack will fail nearly every time.

int *list;

list = malloc(N * sizeof(int));

This puts the allocation on the heap where there is a lot more memory available.