HeavyTailTimeDist.cc

// Copyright 2008 Michael Marsh, University of Maryland.
//
// This file is part of pydtn.
//
// pydtn 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.
//
// pydtn 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 pydtn.  If not, see <http://www.gnu.org/licenses/>.
//
// The views and conclusions contained in the software and documentation
// are those of the authors and should not be interpreted as representing
// official policies, either expressed or implied, of the University
// of Maryland.
//
// pydtn extends and embeds the Python interpreter, which is
// Copyright 2001-2006 Python Software Foundation, All Rights Reserved,
// and is released under the PSF License Agreement.
//
// RANLUX random number generation uses the Boost library,
// Copyright 1994-2006 by various authors (details in individual files),
// which is released under the Boost Software License, Version 1.0.

#include "simlpy/interpreter_hooks.h"
#include "HeavyTailTimeDist.h"
#include <stdlib.h>
#include <math.h>

HeavyTailTimeDist::HeavyTailTimeDist( double alpha ) :
   m_alpha( alpha )
{
}

Time
HeavyTailTimeDist::operator()( const Time& t )
{
   double r = prng() / (1.0 * RAND_MAX);
   double lr = -1.0 * ::log(r) / m_alpha;
   double e = ::exp(lr) - 1;
   long int s = (long int) ::floor(e);
   long int us = (long int)( Time::MILLION * ( e - ::floor(e) ) );
   return ( t + Time(s,us) );
}

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