Random.h

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/*
    liban - base function to do usefull things related to simulation and scientific work
    Copyright (C) 1999-2005 Stephane Magnenat <stephane at magnenat dot net>
    Copyright (c) 2004-2005 Antoine Beyeler <antoine dot beyeler at epfl dot ch>
    Copyright (C) 2005 Laboratory of Intelligent Systems, EPFL, Lausanne
    See AUTHORS for details

    This program 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 2 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#ifndef __AN_RANDOM_H
#define __AN_RANDOM_H

#include <cmath>
#include <cstdlib>

namespace An
{

    class FastRandom
    {
    private:
        unsigned long randx; 
    
    public:
        FastRandom(void) { randx = 0; }
        void setSeed(unsigned long seed) { randx = seed; }
        unsigned long get(void) { return (randx = randx*1103515245 + 12345) & 0x7fffffff; }
        double getRange(double range) { return (static_cast<double>(get()) * range) / 2147483648.0; }
    };
    

    inline double uniformRand(void)
    {
        return double(rand())/RAND_MAX;
    }
    
    struct UniformRand
    {
        double from; 
        double to;
        
        UniformRand(double from = 0.0, double to = 1.0) { this->from = from; this->to = to; }
        
        double operator()() const { return from + (to-from)*uniformRand(); }
    };
    

    inline unsigned intRand(unsigned max)
    {
        if (max)
            return rand() % max;
        else
            return 0;
    }
    

    inline bool boolRand(double prob = 0.5)
    {
        return uniformRand() < prob;
    }
    

    inline double gaussianRand(double mean, double sigm)
    {
        // Generation using the Polar (Box-Mueller) method.
        // Code inspired by GSL, which is a really great math lib.
        // http://sources.redhat.com/gsl/
        // C++ wrapper available.
        // http://gslwrap.sourceforge.net/
        double r, x, y;
        
        // Generate random number in unity circle.
        do
        {
            x = uniformRand()*2 - 1;
            y = uniformRand()*2 - 1;
            r = x*x + y*y;
        }
        while (r > 1.0 || r == 0);
        
        // Box-Muller transform.
        return sigm * y * sqrt (-2.0 * log(r) / r) + mean;
    }
}

#endif

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