satellite-markov-model.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013 Magister Solutions Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * 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
 *
 * Author: Frans Laakso <frans.laakso@magister.fi>
 */
 
#include "satellite-markov-model.h"
 
#include <ns3/log.h>
#include <ns3/simulator.h>
 
#include <cstdlib>
#include <limits>
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(SatMarkovModel);
NS_LOG_COMPONENT_DEFINE("SatMarkovModel");
 
TypeId
SatMarkovModel::GetTypeId(void)
{
    static TypeId tid =
        TypeId("ns3::SatMarkovModel").SetParent<Object>().AddConstructor<SatMarkovModel>();
    return tid;
}
 
SatMarkovModel::SatMarkovModel()
    : m_probabilities(new double[3 * 3]),
      m_numOfStates(3),
      m_currentState(0)
{
    NS_LOG_FUNCTION(this);
 
    NS_FATAL_ERROR("SatMarkovModel::SatMarkovModel - Constructor not in use");
}
 
SatMarkovModel::SatMarkovModel(uint32_t numOfStates, uint32_t initialState)
    : m_probabilities(new double[numOfStates * numOfStates]),
      m_numOfStates(numOfStates),
      m_currentState(initialState)
{
    NS_LOG_FUNCTION(this << numOfStates);
 
    NS_LOG_INFO("Creating Markov model for " << numOfStates
                                             << " states, initial state: " << m_currentState);
 
    for (uint32_t i = 0; i < m_numOfStates; ++i)
    {
        for (uint32_t j = 0; j < m_numOfStates; ++j)
        {
            m_probabilities[i * m_numOfStates + j] = 1;
        }
    }
}
 
SatMarkovModel::~SatMarkovModel()
{
    NS_LOG_FUNCTION(this);
 
    Reset();
}
 
void
SatMarkovModel::DoDispose()
{
    NS_LOG_FUNCTION(this);
 
    Reset();
    Object::DoDispose();
}
 
void
SatMarkovModel::Reset()
{
    NS_LOG_FUNCTION(this);
 
    if (m_probabilities != nullptr)
    {
        delete[] m_probabilities;
        m_probabilities = nullptr;
    }
}
 
uint32_t
SatMarkovModel::GetState() const
{
    NS_LOG_FUNCTION(this);
 
    return m_currentState;
}
 
void
SatMarkovModel::SetState(uint32_t newState)
{
    NS_LOG_FUNCTION(this << newState);
 
    if (newState >= m_numOfStates)
    {
        NS_FATAL_ERROR("SatMarkovModel::SetState - Invalid state");
    }
 
    m_currentState = newState;
}
 
uint32_t
SatMarkovModel::DoTransition()
{
    NS_LOG_FUNCTION(this);
 
    NS_LOG_INFO("Doing transition, current state: " << m_currentState);
 
    double total = 0;
    for (uint32_t i = 0; i < m_numOfStates; ++i)
    {
        total += m_probabilities[m_currentState * m_numOfStates + i];
    }
 
    if ((fabs(total - 1.0) > std::numeric_limits<double>::epsilon()))
    {
        NS_FATAL_ERROR("SatMarkovModel::DoTransition - Probability sum does not match");
    }
 
    double r = total * (std::rand() / double(RAND_MAX));
 
    NS_LOG_INFO("Random value: " << r);
 
    double acc = 0.0;
    for (uint32_t i = 0; i < m_numOfStates; ++i)
    {
        acc += m_probabilities[m_currentState * m_numOfStates + i];
 
        NS_LOG_INFO("State " << i << " accumulated value: " << acc);
 
        if (r <= acc)
        {
            NS_LOG_INFO("Transition done, new state: " << i);
            m_currentState = i;
            return i;
        }
    }
    NS_LOG_INFO("Transition done, new state: " << m_numOfStates - 1);
    m_currentState = m_numOfStates - 1;
    return m_numOfStates - 1;
}
 
void
SatMarkovModel::SetProbability(uint32_t from, uint32_t to, double probability)
{
    NS_LOG_FUNCTION(this << from << " " << to << " " << probability);
 
    NS_LOG_INFO("Setting probability, from: " << from << " to: " << to
                                              << " probability: " << probability);
    m_probabilities[from * m_numOfStates + to] = probability;
}
 
} // namespace ns3