C simulation using array crashes when big number of nodes is used - c

Question

I am trying to run a really simple simulation of infected nodes in a network.
The problem is that when I change the number of nodes to a big one (eg 1.000.000) the executable crashes and the results I get stop at node number 32768.
I guess that it has to do with the maximum number int datatype can store.
Is there any way to avoid this without using malloc?
I have tried to change the datatype from int to double but doesnt seem to help.
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define INFECTED 1
#define HEALTHY 0
#define N 100000
int main(){
srand(time(NULL));
int infected;
int nodes[N] = { HEALTHY };
int totalinfected = 1;
int currentinfected = 1;
nodes [ rand() % N ] = INFECTED;
int timestep = 1;
FILE *ptr;
ptr = fopen ("results.csv", "w+");
while (totalinfected < N) {
for (infected = 1; infected<=currentinfected; infected++) {
int node = rand() % N;
if (nodes[node] == HEALTHY){
nodes[node] = INFECTED;
totalinfected++;
}
}
currentinfected = totalinfected;
fprintf(ptr , "%d; %d\n", timestep, totalinfected);
timestep++;
}
fclose(ptr);
printf("success all infected\n");
return 0;
}

Answer 1

The problem had nothing to do with the maximum number int datatype can store. (which by the way is 2,147,483,647, much larger than your value for N). And, unless you have a very small maximum stack size defined in your environment, I do not think stack size was the problem.
From running your code on my system, it appears that the range of the rand() function was really the culprit. Its range is determined by RAND_MAX, which actual value is implementation specific. In the comments, it was suggested that you check its value. On my system it is defined as:
#define RAND_MAX 32767
As a result, all progress was stopped on my system when 32767 of the 100000 array locations available were processed. The only way to move beyond this point is to have a random number generator with a range sufficient to populate all 100000 locations.
I tested this with a wonky (but in this case effective) modified number generator based on rand():
int a_bigger_rand_max(void)
{
int a, b;
a = rand();
b = rand();
return a*(RAND_MAX+1)+b;
}
Which will generate up to (RAND_MAX+1)^2-1 numbers.
Other than adding this function, and its prototype at top, this was the only line that was changed (in your main() function):
int node = rand() % N;
To:
int node = a_bigger_rand_max() % N;
This resulted in a successful run. (assuming that the criteria for success is the .csv file being populated, and a printout of success all infected\n on teh console.