Re: [Boost-users] Random: How to get a different seed?

Subject: Re: [Boost-users] Random: How to get a different seed?
From: Hernán Leoni (leoni.hernan_at_[hidden])
Date: 2011-01-24 09:33:53

I think you have to use the time as argument for the generator
 mt19937 gen(time(0));

2011/1/24 Zoltán Lengyel <katzlengyel_at_[hidden]>

> Hello,
> I am trying to make a simple program that can generate random integers in
> range, using boost::uniform_int.
>
>
> http://www.boost.org/doc/libs/1_45_0/doc/html/boost_random/tutorial.html#boost_random.tutorial.generating_integers_in_a_range
> This tutorial tells:
> "We use mt19937<http://www.boost.org/doc/libs/1_45_0/doc/html/boost/mt19937.html>with the default seed as a source of randomness. The numbers produced will
> be the same every time the program is run. One common method to change this
> is to seed with the current time (std::time(0) defined in ctime)."
>
> I have trouble getting this common method compile and work. Here's a tiny
> program that works, with the same seed at every run (like what the tutorial
> does), I have commented out my desperate tries to make the seed change.
>
>
> #include "uniform_int.hpp"
> #include "boost/random/variate_generator.hpp"
> #include "boost/random/mersenne_twister.hpp"
> #include <time.h>
>
> #include <iostream>
> using namespace std;
> using namespace boost;
>
> mt19937 gen;
> // time_t gen = time(0);
>
>
> int roll_die()
> {
>     uniform_int<> dist(1, 6);
>     variate_generator<mt19937&, uniform_int<> > die(gen, dist);
>     //boost::variate_generator<time_t, boost::uniform_int<> > die(gen,
> dist);
>     return die();
> }
>
>
> int main()
> {
>     for (int i = 0; i < 5; i++)
>         cout << roll_die() << endl;
>
>     return 0;
> }
>
> So, I would be glad, if someone could fix this for me, to have a different
> seed (depending on system time) at each start.
> Thanks!
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