Code:
/***************************************************************************
* rnd.C
*
* exports: rnd(n) -- returns a "random" integer in {0,1, ..., n-1}
* drnd(r) -- returns a "random" real in [0,r)
*
* P Rogaway - 10/95
*
* NOTE: uses brain-dead mechanisms; These routines are inappropriate for
* applications requiring "unguessable" pseudorandom numbers (e.g., for
* cryptographic purposes).
***************************************************************************
*/
#ifndef IOSTREAMH
#include <iostream.h>
#endif
#ifndef __MATH_H__
#include <math.h>
#endif
#ifndef _SYS_TIME_H
#include <sys/time.h>
#endif
#ifndef __STDLIB_H__
#include <stdlib.h>
#endif
#ifndef _SGI_SOURCE
extern "C" int gettimeofday(struct timeval *tp,struct timezone *tz);
#endif
static const same_random_numbers_each_run = 0; // for debug, sometimes useful
// to set this to 1, so one
// always gets the same
// "random" numbers.
/*
* getseed
* get a seed (just 32 bits) for the pseudorandom generator, using
* the simplest possible thing (time returned by gettimeofday()).
*/
static long getseed()
{
if (same_random_numbers_each_run) {
return 1;
}
else {
struct timeval tp;
struct timezone tzp;
if (gettimeofday(&tp, &tzp)) {
cerr << "getseed: gettimeofday failed\n";
return 0;
}
return tp.tv_usec;
}
}
///////////////////////////////////////////////////////////
// rnd(n) -- return a "random" integer in [0..n-1]
///////////////////////////////////////////////////////////
int rnd(int n)
{
static first_time=1;
static char state[256];
if (first_time) {
first_time = 0;
unsigned int seed = (unsigned int) getseed();
initstate(seed, state, 256);
}
if (n<0) {cerr << "Bad argument to rnd()\n"; return 0;}
unsigned long mask = 1;
while (mask<n) mask = 2*mask+1;
for (;;) {
long r = random();
if ((r&mask) < n) return r&mask;
}
}
///////////////////////////////////////////////////////////
// drnd(r) -- return a "random" double in [0,.r)
///////////////////////////////////////////////////////////
double drnd(double r)
{
static first_time=1;
if (first_time) {
first_time = 0;
long seed = long(getseed());
srand48(seed);
}
return r*drand48();
}
random brojevi ~ kako najbrze i najlakshe ?
