Re: [boost] Problem with boost::random seed

Subject: Re: [boost] Problem with boost::random seed
From: Anton Skvorts (anton.skvorts_at_[hidden])
Date: 2011-01-27 22:10:16

Oh, although the code was run with just one variate_generator, I
transcribed in my post one line of the code erroneously:

where is die(gen, normal) it should be rng(gen, normal)

Anyway I got that strange output using just one variate_generator everywhere:
variate_generator<std::mt19937 &,std::normal_distribution<> > rng(gen, normal);

Steven, does your comment still applies in this case?

2011/1/28 Steven Watanabe <watanabesj_at_[hidden]>:
> AMDG
>
> On 1/27/2011 6:18 PM, Anton Skvorts wrote:
>>
>> I'm still having some problems with boost::random, obviously because I
>> don't fully understand all that s going on... Read the documentation
>> and  your post but still cannot find what is wrong with my code
>> bellow:
>>
>
> Notice that you have two separate variate_generators,
> one in the main code, and one for each call to normalReseed.
> Each normal_distribution object has its own cache.
> When you call reset, you need to make sure that
> you call it on the distribution that you are using.
>
>> extern "C" __declspec(dllexport) double normalReseed(double mean,
>>    double sigma, uint32_t x){
>>  boost::normal_distribution<>  normal(mean,sigma);
>>  boost::variate_generator<boost::mt19937&,
>>    boost::normal_distribution<> > rng(gen, normal);
>>  rng.engine().seed(x);
>>  rng.distribution().reset();
>>  return rng();
>> }
>> boost::mt19937 gen;
>> boost::normal_distribution<>  normal(0,1);
>> boost::variate_generator<boost::mt19937&,
>>    boost::normal_distribution<> > die(gen, normal);
>> cout<<  rng()<<  endl;
>> cout<<  rng()<<  endl;
>> cout<<  rng()<<  endl;
>> cout<<  normalReseed(0, 1, 0)<<  endl;
>> cout<<  rng()<<  endl;
>> <snip>
>>
>> Possibly are again cached results from Box-Muller algorithm the reason
>> for this pattern but still cannot see why we get these results,
>> neither how to overcome this problem
>>
>
> In Christ,
> Steven Watanabe
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