How to create vector of variate_generator?

Question

I'm trying to create a vector of boost random number generators.

I've tried creating function pointers to the variate_generators without much luck either.

#include <iostream>
#include <boost/random.hpp>

using namespace std;

int main(int argc, const char *argv[])
{
    const double mean = 0.0;
    const double sigma = 1.0;

    // Setup aliases
    typedef boost::normal_distribution<> NormalDistribution;
    typedef boost::mt19937 RandomNumberGenerator;
    typedef boost::variate_generator<RandomNumberGenerator&, NormalDistribution> NormalGenerator;

    vector<NormalGenerator> gen_vec;

    RandomNumberGenerator rng;
    rng.seed(12345);

    NormalDistribution noise_distribution(mean, sigma);

    NormalGenerator rng_eng(rng, noise_distribution); // create RNG

    gen_vec.push_back(rng_eng);

    return 0;
}

I was hoping to use gen_vec to get a function in order to generate a random number for a given element in the vector. But when I attempt to compile it throws this error.

/usr/include/boost/random/detail/pass_through_engine.hpp:27: error: non-static reference member \u2018main(int, const char**)::RandomNumberGenerator& boost::random::detail::pass_through_engine<main(int, const char**)::RandomNumberGenerator&>::_rng\u2019, can't use default assignment operator

I'm guessing that's because I'm not packing the variate_generators correctly.

Is what I'm trying to do correct much less possible?

Answer 1

At first, your example code does compile without any error message (GCC 8.2.1, boost 1.69).

But, don't do that. Just use boost::variate_generator<>::distribution() to set a new distribution.

NormalDistribution noise_distribution(mean, sigma);
NormalDistribution other_distribution(5.0, 2.0);
NormalGenerator rng_eng(rng, noise_distribution); // create RNG
// ... generate RNG using noise_distribution
rng_eng.distribution() = other_distribution;
// ... generate RNG using other_distribution
rng_eng.distribution() = noise_distribution;
// ... generate RNG using noise_distribution again