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Pareto.cpp

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 * This file is part of openWNS (open Wireless Network Simulator)
 * _____________________________________________________________________________
 *
 * Copyright (C) 2004-2007
 * Chair of Communication Networks (ComNets)
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 * fax: ++49-241-80-22242
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 * openWNS is free software; you can redistribute it and/or modify it under the
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 * Free Software Foundation;
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 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 * A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
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#include <WNS/distribution/Pareto.hpp>

#include <limits>


using namespace wns::distribution;

STATIC_FACTORY_REGISTER_WITH_CREATOR(
    Pareto,
    Distribution,
    "Pareto",
    wns::PyConfigViewCreator);
STATIC_FACTORY_REGISTER_WITH_CREATOR(
    Pareto,
    Distribution,
    "Pareto",
    wns::distribution::RNGConfigCreator);

Pareto::Pareto(double shapeA, double scaleB, wns::rng::RNGen* rng) :
    Distribution(rng),
    shapeParamA_(shapeA),
    scaleParamB_(scaleB),
    dis_(getRNG())
{
    assert(shapeParamA_ > 0.0);
    assert(scaleParamB_ >= 0.0);
}

Pareto::Pareto(const pyconfig::View& config) :
    Distribution(),
    shapeParamA_(config.get<double>("shapeA")),
    scaleParamB_(config.get<double>("scaleB")),
    dis_(getRNG())
{
    assert(shapeParamA_ > 0.0);
    assert(scaleParamB_ >= 0.0);
}

Pareto::Pareto(wns::rng::RNGen* rng, const pyconfig::View& config) :
    Distribution(rng),
    shapeParamA_(config.get<double>("shapeA")),
    scaleParamB_(config.get<double>("scaleB")),
    dis_(getRNG())
{
    assert(shapeParamA_ > 0.0);
    assert(scaleParamB_ >= 0.0);
}


Pareto::~Pareto()
{
}


double
Pareto::operator()()
{
    double f = 0.0;
    double x = scaleParamB_;
    // Avoid endless loops
    unsigned long int max_num_loops = 1000; 
    
    while (max_num_loops--)
    {
        f = dis_();
        assert(0.0 <= f && f <= 1.0);
        if (f == 1.0)
        {
            continue;
        }
        x = scaleParamB_ / pow(1.0 - f, 1.0 / shapeParamA_);
        return x;
    }
    assure(false, "Something very unlikely happened.");
    return x;
}

double
Pareto::getMean() const
{
    if (shapeParamA_ <= 1.0)
    {
        return std::numeric_limits<double>::max();
    }

    return shapeParamA_ * scaleParamB_ / (shapeParamA_ - 1.0);
}

std::string
Pareto::paramString() const
{
    std::ostringstream tmp;
    tmp << "Pareto(A=" << shapeParamA_ << ",B=" << scaleParamB_ << ")";
    return tmp.str();
}

/*
  Local Variables:
  mode: c++
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  c-tab-always-indent: t
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  End:
*/

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