Classes | Public Member Functions | Protected Member Functions | Private Attributes

ParetoChurn Class Reference

Lifetime churn based on shifted pareto distribution. More...

#include <ParetoChurn.h>

Inheritance diagram for ParetoChurn:
ChurnGenerator

List of all members.

Classes

struct  node_stat

Public Member Functions

void handleMessage (cMessage *msg)
void initializeChurn ()
 ParetoChurn ()
 ~ParetoChurn ()

Protected Member Functions

void updateDisplayString ()
void createNode (double lifetime, double meanLifetime, double meanDeadtime, bool initialize)
void deleteNode (TransportAddress &addr, double meanLifetime, double meanDeadtime)
double shiftedPareto (double a, double b, int rng=0)
 implements a shifted pareto funcion
double betaByMean (double mean, double alpha=3)
 returns a shifted pareto function's beta param by given mean and alpha
double individualMeanTime (double mean)
 returns the individual mean life/dead time of a node
double individualLifetime (double mean)
 returns a individual lifetime (or deadtime) based on a node's mean lifetime
double residualLifetime (double mean)
 returns the resiidual lifetime (or deadtime) based on a node's mean lifetime
void scheduleCreateNodeAt (double creationTime, double lifetime, double meanLifetime, double meanDeadtime)

Private Attributes

GlobalStatistics * globalStatistics
double initialMean
 mean of update interval during initalization phase
double initialDeviation
 deviation of update interval during initalization phase
double lifetimeMean
 mean node lifetime
double deadtimeMean
 mean node deadtime
simtime_t lastCreatetime
simtime_t lastDeletetime
cMessage * initFinishedTimer
 timer to signal end of init phase

Detailed Description

Lifetime churn based on shifted pareto distribution.

This class implements the curn model proposed in

Yao, Z.; Leonard, D.; Wang, X. & Loguinov, D. "Modeling Heterogeneous User Churn and Local Resilience of Unstructured P2P Networks" Proceedings of the 2006 14th IEEE International Conference on Network Protocols, 2006. ICNP '06. 2006, pp. 32--41

Definition at line 46 of file ParetoChurn.h.

Constructor & Destructor Documentation

ParetoChurn::ParetoChurn (  )  [inline]

Definition at line 51 of file ParetoChurn.h.

{ initFinishedTimer = NULL; };

ParetoChurn::~ParetoChurn (  ) 

Definition at line 247 of file ParetoChurn.cc.

                          {
    // destroy self timer messages
    cancelAndDelete(initFinishedTimer);
}

Member Function Documentation

double ParetoChurn::betaByMean ( double  mean,
double  alpha = 3 
) [protected]

returns a shifted pareto function's beta param by given mean and alpha

Parameters:
mean the wanted mean
alpha the alph param of the shifted pareto (defaults to 3)
Returns:
the beta parameter

Definition at line 209 of file ParetoChurn.cc.

Referenced by individualLifetime(), individualMeanTime(), and residualLifetime().

{
    return 1/(mean*(alpha -1));
}

void ParetoChurn::createNode ( double  lifetime,
double  meanLifetime,
double  meanDeadtime,
bool  initialize 
) [protected]

Definition at line 162 of file ParetoChurn.cc.

Referenced by handleMessage().

{
    ParetoChurnMessage* churnMsg = new ParetoChurnMessage("DeleteNode");
    TransportAddress* ta = underlayConfigurator->createNode(type, initialize);
    churnMsg->setAddr(*ta);
    delete ta;
    churnMsg->setCreateNode(false);
    churnMsg->setMeanLifetime(meanLifetime);
    churnMsg->setMeanDeadtime(meanDeadtime);
    scheduleAt(std::max(simTime(), simTime() + lifetime
                   - underlayConfigurator->getGracefulLeaveDelay()), churnMsg);

    RECORD_STATS(globalStatistics->recordOutVector("ParetoChurn: Session Time",
                                                   lifetime));

    RECORD_STATS(globalStatistics->recordOutVector("ParetoChurn: "
                 "Time between creates", SIMTIME_DBL(simTime() - lastCreatetime)));

    lastCreatetime = simTime();
}

void ParetoChurn::deleteNode ( TransportAddress &  addr,
double  meanLifetime,
double  meanDeadtime 
) [protected]

Definition at line 184 of file ParetoChurn.cc.

Referenced by handleMessage().

{
    // Kill node
    underlayConfigurator->preKillNode(NodeType(), &addr);

    RECORD_STATS(globalStatistics->recordOutVector("ParetoChurn: "
               "Time between deletes", SIMTIME_DBL(simTime() - lastDeletetime)));
    lastDeletetime = simTime();
    scheduleCreateNodeAt(SIMTIME_DBL(simTime()+individualLifetime(meanDeadtime)),
                         individualLifetime(meanLifetime), meanLifetime,
                         meanDeadtime);
}

void ParetoChurn::handleMessage ( cMessage *  msg  )  [virtual]

Implements ChurnGenerator.

Definition at line 132 of file ParetoChurn.cc.

{
    if (!msg->isSelfMessage()) {
        delete msg;
        return;
    }

    // init phase finished
    if (msg ==  initFinishedTimer) {
        underlayConfigurator->initFinished();
        cancelEvent(initFinishedTimer);
        delete initFinishedTimer;
        initFinishedTimer = NULL;

        return;
    }

    ParetoChurnMessage* churnMsg = check_and_cast<ParetoChurnMessage*>(msg);

    if (churnMsg->getCreateNode() == true) {
        createNode(churnMsg->getLifetime(), churnMsg->getMeanLifetime(),
                   churnMsg->getMeanDeadtime(), false);
    } else {
        deleteNode(churnMsg->getAddr(), churnMsg->getMeanLifetime(),
                   churnMsg->getMeanDeadtime());
    }

    delete msg;
}

double ParetoChurn::individualLifetime ( double  mean  )  [protected]

returns a individual lifetime (or deadtime) based on a node's mean lifetime

Parameters:
mean the node's men lifetime
Returns:
the lifetime

Definition at line 227 of file ParetoChurn.cc.

Referenced by deleteNode(), and initializeChurn().

{
    return shiftedPareto(3, betaByMean(mean));
}

double ParetoChurn::individualMeanTime ( double  mean  )  [protected]

returns the individual mean life/dead time of a node

Parameters:
mean the global mean life/dead time
Returns:
the mean life/dead time of the node

Definition at line 221 of file ParetoChurn.cc.

Referenced by initializeChurn().

{
//    return shiftedPareto(3, betaByMean(mean*exp(1)));
    return shiftedPareto(3, betaByMean(mean));
}

void ParetoChurn::initializeChurn (  )  [virtual]

Implements ChurnGenerator.

Definition at line 44 of file ParetoChurn.cc.

{
    Enter_Method_Silent();

    initialMean = par("initPhaseCreationInterval");
    initialDeviation = initialMean / 3;
    lifetimeMean = par("lifetimeMean");
    deadtimeMean = par("deadtimeMean");

    WATCH(lifetimeMean);
    WATCH(deadtimeMean);

    lastCreatetime = 0;
    lastDeletetime = 0;

    globalStatistics = GlobalStatisticsAccess().get();

    double initFinishedTime = initialMean * targetOverlayTerminalNum;

    // try to create a stable equilibrium of nodes in init phase
    //
    // check for each node if he is present in initial state
    // and roll individual mean life+dead times
    int liveNodes = 0;
    double sum_l_i = 0;
    std::deque<node_stat> node_stats;

    for (int i = 0; liveNodes < (int)par("targetOverlayTerminalNum"); i++) {

        double nodeLifetimeMean = individualMeanTime(lifetimeMean);
        globalStatistics->recordOutVector("ParetoChurn: Node individual "
                                          "mean lifetime", nodeLifetimeMean);
        double nodeDeadtimeMean = individualMeanTime(deadtimeMean);
        globalStatistics->recordOutVector("ParetoChurn: Node individual "
                                          "mean deadtime", nodeDeadtimeMean);
        sum_l_i += 1.0/(nodeLifetimeMean + nodeDeadtimeMean);
        node_stat nodeStat;
        nodeStat.l = nodeLifetimeMean;
        nodeStat.d = nodeDeadtimeMean;
        double nodeAvailability = nodeLifetimeMean/(nodeLifetimeMean
                                                    + nodeDeadtimeMean);

        globalStatistics->recordOutVector("Node availability", nodeAvailability);

        nodeStat.alive = uniform(0, 1) < nodeAvailability;
        if (nodeStat.alive) {
            liveNodes++;
        }
        node_stats.push_back( nodeStat );
    }

    // compute "stretch" factor to reach the configured average lifetime
    // this is neccessary as "individual" lifetime mean has to be bigger than
    // "global" lifetime mean, as short-lived nodes will factor in more often
    double mean_life = 0;
    int numNodes = node_stats.size();
    for( int i = 0; i < numNodes; ++i ){
        node_stat& stat = node_stats[i];
        mean_life += stat.l/( (stat.l + stat.d) * sum_l_i );
    }
    double stretch = lifetimeMean/mean_life;
    liveNodes = 0;

    // schedule creation for all (alive or dead) nodes
    for( int i = 0; i < numNodes; ++i ){
        node_stat& stat = node_stats.front();
        stat.l *= stretch;
        stat.d *= stretch;

        if( stat.alive ){
            double scheduleTime = truncnormal(initialMean*liveNodes, initialDeviation);
            scheduleCreateNodeAt(scheduleTime, initFinishedTime - scheduleTime
                                 + residualLifetime(stat.l),
                                 stat.l, stat.d);
            liveNodes++;
        } else {
            scheduleCreateNodeAt(initFinishedTime
                                 + residualLifetime(stat.d),
                                 individualLifetime(stat.l),
                                 stat.l, stat.d);
        }
        node_stats.pop_front();
    }

    initFinishedTimer = new cMessage("initFinishTimer");
    scheduleAt(initFinishedTime, initFinishedTimer);
}

double ParetoChurn::residualLifetime ( double  mean  )  [protected]

returns the resiidual lifetime (or deadtime) based on a node's mean lifetime

Parameters:
mean the node's men lifetime
Returns:
the residual lifetime

Definition at line 235 of file ParetoChurn.cc.

Referenced by initializeChurn().

{
    return shiftedPareto(2, betaByMean(mean));
}

void ParetoChurn::scheduleCreateNodeAt ( double  creationTime,
double  lifetime,
double  meanLifetime,
double  meanDeadtime 
) [protected]

Definition at line 198 of file ParetoChurn.cc.

Referenced by deleteNode(), and initializeChurn().

{
    ParetoChurnMessage* churnMsg = new ParetoChurnMessage("CreateNode");
    churnMsg->setCreateNode(true);
    churnMsg->setLifetime(lifetime);
    churnMsg->setMeanLifetime(meanLifetime);
    churnMsg->setMeanDeadtime(meanDeadtime);
    scheduleAt(creationTime, churnMsg);
}

double ParetoChurn::shiftedPareto ( double  a,
double  b,
int  rng = 0 
) [protected]

implements a shifted pareto funcion

Definition at line 214 of file ParetoChurn.cc.

Referenced by individualLifetime(), individualMeanTime(), and residualLifetime().

{
    // What OMNET calles "pareto_shifted" in reality is a gerneralized pareto,
    // not a shifted pareto...
    return (pareto_shifted(a, b, 0, rng)/b - 1) / b;
}

void ParetoChurn::updateDisplayString (  )  [protected, virtual]

Implements ChurnGenerator.

Definition at line 240 of file ParetoChurn.cc.

{
    char buf[80];
    sprintf(buf, "pareto churn");
    getDisplayString().setTagArg("t", 0, buf);
}

Member Data Documentation

double ParetoChurn::deadtimeMean [private]

mean node deadtime

Definition at line 107 of file ParetoChurn.h.

Referenced by initializeChurn().

GlobalStatistics* ParetoChurn::globalStatistics [private]

Definition at line 102 of file ParetoChurn.h.

Referenced by createNode(), deleteNode(), and initializeChurn().

cMessage* ParetoChurn::initFinishedTimer [private]

timer to signal end of init phase

Definition at line 112 of file ParetoChurn.h.

Referenced by handleMessage(), initializeChurn(), ParetoChurn(), and ~ParetoChurn().

double ParetoChurn::initialDeviation [private]

deviation of update interval during initalization phase

Definition at line 105 of file ParetoChurn.h.

Referenced by initializeChurn().

double ParetoChurn::initialMean [private]

mean of update interval during initalization phase

Definition at line 104 of file ParetoChurn.h.

Referenced by initializeChurn().

simtime_t ParetoChurn::lastCreatetime [private]

Definition at line 109 of file ParetoChurn.h.

Referenced by createNode(), and initializeChurn().

simtime_t ParetoChurn::lastDeletetime [private]

Definition at line 110 of file ParetoChurn.h.

Referenced by deleteNode(), and initializeChurn().

double ParetoChurn::lifetimeMean [private]

mean node lifetime

Definition at line 106 of file ParetoChurn.h.

Referenced by initializeChurn().

The documentation for this class was generated from the following files:
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