Re: [boost] Boost.Random.uniform_01 gives different number sequence in Boost 1.37 and Boost 1.45

Subject: Re: [boost] Boost.Random.uniform_01 gives different number sequence in Boost 1.37 and Boost 1.45
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-11-16 10:51:54

AMDG

On 11/16/2011 05:28 AM, Martin.Sovik_at_[hidden] wrote:
> Hi.
> It seems that uniform_01 generates different number sequences in version 1.37 and 1.45
> Is this intentional, or is it a bug?
> 

This change is intentional.  Here's what's happening:

In 1.37, constructing uniform_generator calls seed
to initialize the generator.  In 1.45, it calls the
copy constructor.  Thus, the stored generator ends
up in a different state.  To get the old behavior
add

uniform_generator.base().seed(random_generator);

> This short program
> 
> 
> #include <iostream>
> #include "boost/random/mersenne_twister.hpp"
> #include "boost/random/uniform_01.hpp"
> int main() {
> boost::mt19937 random_generator(4315);
> boost::uniform_01< boost::mt19937, double > uniform_generator(random_generator);
> std::cout<<"Generating uniform distribution using Boost 1.45"<<std::endl;
> for (int i=0; i<10;++i) {
> std::cout<<uniform_generator()<<std::endl;
> }
> return 0;
> }
> 
> Compiled with the two versions, gives the respective output:
> 
> 
> D:\dev\test_bed>uniform_dist_boost_1_37
> Generating uniform distribution using Boost 1.37
> 0.239136
> 0.920749
> 0.889477
> 0.208172
> 0.169688
> 0.636659
> 0.78322
> 0.915117
> 0.25697
> 0.358218
> D:\dev\\test_bed>uniform_dist_boost_1_45
> Generating uniform distribution using Boost 1.45
> 0.306389
> 0.511291
> 0.496429
> 0.156168
> 0.910315
> 0.644836
> 0.331514
> 0.558632
> 0.723934
> 0.998796
> 
> As far as I can tell, Boost.mt19937 gives the same number sequence in both cases, but the output from Boost.uniform_01 differs.
> 
> This topic has been briefly touched in the thread
> 
> [boost] Random numbers question<154235.php> Anant Rao (2009-07-24 18:47:31)
> Where it seems like Rao got different numbers even between Boost 1.38 and Boost 1.39
> 
> We use Boost 1.37 in the previous release of our software, and Boost 1.45 in the current, and we have received a bug report from one of our clients that our current release has different behaviour.
> Is there any way to fix this, other than use the 1.37 version of Boost.uniform_01?
> 

In Christ,
Steven Watanabe