The following program:
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>
int main()
{
int i=0;
int j=rand();
while (rand()!=j) i++;
printf("%d\n",i);
return 0;
}
gives the following output:
-1406966551
>From this, can I find out when the numbers start repeating? How can I find it? I cannot find the period using
man rand
Anna
----- Original Message -----
From: Marc Glisse <marc.glisse@xxxxxxxx>
Date: Saturday, August 6, 2011 7:34 pm
Subject: Re: question on rand()
> On Sat, 6 Aug 2011, Andrew Haley wrote:
>
> > On 08/06/2011 08:47 AM, Anna Sidera wrote:
> >> Hello,
> >>
> >> I am using gcc on a unix machine. Can you tell me how many
> random numbers can be generated using
> >>
> >> rand()
> >>
> >> before the random numbers start repeating?
>
> man rand
> If it's not there, complain to your unix vendor.
> The period is required by posix to be larger or equal to 2^32.
>
> > One would hope it has full period, i.e. it generates all
> RAND_MAX numbers,
> > but that depends on your system.
>
> One would even hope the period is larger, so the output of rand()
> is not a
> deterministic function of its last return value (random generators
> often
> keep a hidden state).
>
> --
> Marc Glisse
>
