CODEWITHSUNDEEP
c++randomboostc++98
Riptyde4
Riptyde4

Reputation: 5460

Boost Random Generators returning identical values

WITHOUT USING C++ 11 RANDOM

Looking for a boost random expert... I need to generate random numbers in between many, many different ranges. I've written the below functions:

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

boost::mt19937 g_oRng;

int generateIntVariate(int p_iMin, int p_iMax){
  boost::uniform_int<> min_to_max(p_iMin, p_iMax);
  boost::variate_generator< boost::mt19937, boost::uniform_int<> > oGen(g_oRng, min_to_max);
  return oGen();
}

float generateFloatVariate(int p_fMin, p_fMax){
  boost::uniform_real<> min_to_max(p_fMin, p_fMax);
  boost::variate_generator< boost::mt19937, boost::uniform_real<> > oGen(m_oRng, min_to_max);
  return oGen();
}


int main(){
  struct timeval tp;
  gettimeofday(&tp, NULL);
  g_oRng = boost::mt19937((int)tp.tv_sec);


  for(int i = 0 ; i < 10 ; ++i){
    std::cout << generateIntVariate(0, 10) << ", " << generateFloatVariate(0.0f, 10.0f) << std::endl;
  }
}

The problem is that both functions return the same exact number for a given range, every time it's executed.

(gdb) p generateIntVariate(0, 10)
$40 = 8
(gdb) p generateIntVariate(0, 10)
$41 = 8
(gdb) p generateIntVariate(0, 10)
$42 = 8
(gdb) p generateIntVariate(0, 10)
$43 = 8

The same thing as above happens with the float function. Is there any way I can accomplish what I'm trying to do using the boost random distros?

Upvotes: 0

Views: 109

Answers (1)

LogicStuff
LogicStuff

Reputation: 19607

boost::variate_generator's constructor looks like this:

variate_generator(Engine e, Distribution d);

- meaning it won't change the state of passed-in m_oRng and makes a copy of it instead.

I suggest omitting variate_generator and just using boost::uniform_int<>::operator().

Upvotes: 4

Related Questions