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/**************************************************************************/
/* Copyright 2012 Tim Day */
/* */
/* This file is part of Evolvotron */
/* */
/* Evolvotron is free software: you can redistribute it and/or modify */
/* it under the terms of the GNU General Public License as published by */
/* the Free Software Foundation, either version 3 of the License, or */
/* (at your option) any later version. */
/* */
/* Evolvotron is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
/* GNU General Public License for more details. */
/* */
/* You should have received a copy of the GNU General Public License */
/* along with Evolvotron. If not, see <http://www.gnu.org/licenses/>. */
/**************************************************************************/
/*! \file
\brief Interfaces for class Random and derived classes.
*/
#ifndef _random_h_
#define _random_h_
#include "common.h"
//! Abstract base class for random number generation
class Random
{
public:
//! Constructor (nothing to do in base class)
Random()
{}
//! Trivial destructor.
virtual ~Random()
{}
//! Return a random number.
/*! \warning Returns double instead of real because suspect NegExp can return Inf otherwise.
*/
virtual double operator()()
=0;
};
//! Generates random numbers in the range [0,1).
class Random01 : public Random
{
public:
//! Constructor
Random01(uint seed);
//! Trivial destructor
virtual ~Random01();
//! Return next number in sequence.
virtual double operator()();
private:
//! Base generator
boost::mt19937 _rng;
//! Distribution
boost::uniform_real<> _dist;
//! Actual generator
boost::variate_generator<boost::mt19937,boost::uniform_real<> > _gen;
};
//! Return negative-exponentially distributed random numbers.
class RandomNegExp : public Random
{
protected:
//! Underlying generator.
Random01 _generator;
//! Mean value of distribution.
double _mean;
public:
//! Construct generator of numbers with mean value m.
RandomNegExp(uint seed,double m)
:_generator(seed)
,_mean(m)
{}
//! Trivial destructor.
virtual ~RandomNegExp()
{}
//! Return next number in sequence.
virtual double operator()()
{
return -_mean*log(1.0-_generator());
}
};
template <typename T> void random_shuffle(boost::ptr_vector<T>& v,Random01& r01)
{
boost::ptr_vector<T> nv;
while (!v.empty())
{
const uint n=static_cast<uint>(r01()*v.size());
nv.transfer(nv.end(),v.begin()+n,v);
}
v.transfer(v.end(),nv.begin(),nv.end(),nv);
}
//! Adapter to use our random number generator to feed std::random_shuffle
class RandomInt
{
public:
RandomInt(Random01& r01)
:_r01(r01)
{}
uint operator()(uint n)
{
return static_cast<uint>(_r01()*n);
}
private:
Random01& _r01;
};
template <typename T> void random_shuffle(std::vector<T>& v,Random01& r01)
{
RandomInt r0n(r01);
std::random_shuffle(v.begin(),v.end(),r0n);
}
#endif
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