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Controller.java
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Controller.java
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/**
* Generates an LDPC code pair by Gallager or PEG algorithm.
* A modified PEG algorithm is introduced; this can generate irregular graphs.
* Generator class has been made more uniform with the addition of init(int,int,int) abstract method.
* Simulates a BEC, and decodes the all zero code word.
* Computes the colum rank of H2 corresponding to the stopping set in H1.
* Repeats the experimet a number of times for each probability & finds cumulative/ average values.
* Detects the threshold of the code H1, zooms in with fine grained probability step, and repeats the trials.
* Logs all results in a CSV file that can be exported to XL
* @author Rajaraman
*/
import java.util.BitSet;
import java.util.Calendar;
public class Controller
{
Initializer ini;
Logger logger;
long snapShotTime;
float errorKneeProb; // the prob at which decoding errors start appearing for the first time
float errorPlateuProb; // where 90% of decoding attempts fail
public static void main (String[] args) throws Exception
{
long startTime = Calendar.getInstance().getTimeInMillis();
Controller c = new Controller();
c.init("settings.txt");
c.runSimulation();
// the time in the Calendar object is FROZEN at the time of calling getInstance()
long endTime = Calendar.getInstance().getTimeInMillis();
long elapsed = endTime-startTime;
G.itraceln("\nTotal Duration: "+elapsed/1000 +"." +elapsed%1000 +" sec");
c.close();
G.itrace ("Done !");
}
public void close()
{
logger.close();
}
public void init(String iniFileName) throws Exception
{
this.ini = new Initializer();
ini.init(iniFileName);
logger = new Logger();
logger.init();
}
public void runSimulation()throws Exception
{
CodeFactory factory = new CodeFactory();
factory.init (ini);
timeStamp();
Generator g = factory.getGenerator(0);
g.generate();
G.itraceln(g.toString());
logger.logln(g.toString());
logger.clogln(g.toString());
timeStamp("Generated Code 1");
Generator g2 = factory.getGenerator(1);
g2.generate();
G.itraceln(g2.toString());
logger.logln(g2.toString());
logger.clogln(g2.toString());
timeStamp("Generated Code 2");
logger.logln ("EPROB,ECNT,RSLT,SSIZE,COLRNK");
logger.clogln ("EPROB,DELTA,SSIZE,COLRNK");
runSimulation (g, g2, ini.getStartProb(),ini.getEndProb(),ini.getProbStep(),ini.getTrialCount());
// runSimulation sets the knee and plateu probabilities
G.itraceln ("Error knee =" +errorKneeProb);
G.itraceln ("Error plalteau =" +errorPlateuProb);
logger.clogln ("Error knee =" +errorKneeProb);
logger.clogln ("Error plalteau =" +errorPlateuProb);
if (errorPlateuProb-errorKneeProb < ini.getProbStep())
{
G.itraceln ("-- Default Error knee is too small --");
errorKneeProb -= ini.getProbStep();
errorPlateuProb += ini.getProbStep();
}
logger.logln("Zoom");
logger.clogln("Zoom");
//float step = ini.getZoomProbStep();
float step = (errorPlateuProb-errorKneeProb)/10.0f;
G.itraceln ("Zoom probability step = "+step);
runSimulation (g, g2, errorKneeProb, errorPlateuProb,step,ini.getZoomTrialCount());
// runSimulation sets the knee and plateu probabilities
G.itraceln ("Error knee =" +errorKneeProb);
G.itraceln ("Error plateau =" +errorPlateuProb);
logger.clogln ("Error knee =" +errorKneeProb);
logger.clogln ("Error plateau =" +errorPlateuProb);
}
/**
* Runs one complete cycle of simulation for a range of probabilities
* Note: This function sets the class variables errorKneeProb and errorPlateuProb
* @throws Exception
*/
protected void runSimulation (Generator g, Generator g2, float startProb, float endProb, float probStep, int numTrials) throws Exception
{
Channel chl = new Channel();
chl.init(g.getColCount());
Matrix mat = new Matrix();
Matrix mat2 = new Matrix();
TannerGraph tg = new TannerGraph();
BitSet data = new BitSet(g.getColCount());
timeStamp();
boolean allTrialsSucceeded = true; // flags to detect threshold
boolean allTrialsFailed = false;
for (float errProb=startProb; errProb < endProb; errProb = addRoundOff(errProb,probStep))
{
G.itraceln ("\nerror prob= " +errProb);
int stopSetSize = 0;
int columnRank = 0;
int failureCount = 0;
int repeatCount = 0;
for (int trial=0; trial<numTrials; trial++)
{
// NOTE : matrix and tannergraph have to be initiated every time,
// because the bitset is destroyed by rank finding
mat.init(g.getRowCount(), g.getColCount(), g.exportToBitSet());
mat2.init(g2.getRowCount(), g2.getColCount(), g2.exportToBitSet());
tg.init (mat);
data.clear(); // all-zero code word
tg.setData(data);
chl.setErasureProbability(errProb);
tg.setErasures(chl.getErasures());
//tg.dumpMatrix();
boolean result = tg.decode();
logger.log(chl.getErasureProbability());
logger.log(chl.getErasureCount());
if (result)
{
repeatCount = 0;
G.traceln ("Decoded successfully");
logger.log ("success");
}
else
{
if (G.ARQ_MODE && repeatCount < G.MAX_ARQ)
{
repeatCount++;
trial--; // that is all needed for ARQ !
G.itrace ("* ");
}
else
{
repeatCount=0; // maximum ARQ attempts exceeded
failureCount++;
G.traceln ("Decoding failed");
logger.log ("failure");
BitSet colmask = tg.getErasures();
int ssSize = colmask.cardinality();
stopSetSize += ssSize;
G.traceln ("Stopping set (cardinality=" +ssSize +")");
//G.traceln (colmask.toString());
logger.log (ssSize);
mat2.selectColumns(colmask); // the original H is DESTROYED
int rank = mat2.getRank(); // the original H is DESTROYED
columnRank += rank;
G.traceln ("Rank of stopping set colums=" +rank);
logger.log(rank);
}
}
logger.logln();
//G.activity();
} // for- trial
stopSetSize = (int)((float)stopSetSize/numTrials +0.5); // average stopping set size over the trials
columnRank = (int)((float)columnRank/numTrials +0.5); // average col rank
logger.clog(errProb);
logger.clog(errProb-startProb);
logger.clog(stopSetSize);
logger.clogln (columnRank);
if (allTrialsSucceeded && failureCount > 0) // we got the first taste of failure now
{
this.errorKneeProb = errProb;
allTrialsSucceeded = false;
}
if (!allTrialsFailed && failureCount > 0.9*numTrials)
{
this.errorPlateuProb = errProb;
allTrialsFailed = true;
}
} // for- error probability
timeStamp("End of Simulation Runs");
}
private static float addRoundOff (float a, float b)
{
double DELTA = 0.0005;
double sum = a+b+DELTA;
int tmp = (int)(sum*1000);
return (float) tmp/1000.0f;
}
public void timeStamp ()
{
snapShotTime = Calendar.getInstance().getTimeInMillis();
}
public void timeStamp (String context)
{
long currentTime = Calendar.getInstance().getTimeInMillis();
long elapsed = currentTime-snapShotTime;
G.itraceln("\n" +context +": "+ elapsed/1000 +"." +elapsed%1000 +" sec");
snapShotTime = currentTime;
}
}