/**
* Get a path from the local FS. If size is known, we go round-robin over the set of disks (via
* the configured dirs) and return the first complete path which has enough space.
*
* <p>If size is not known, use roulette selection -- pick directories with probability
* proportional to their available space.
*/
public synchronized Path getLocalPathForWrite(
String pathStr, long size, Configuration conf, boolean checkWrite) throws IOException {
confChanged(conf);
int numDirs = localDirsPath.length;
int numDirsSearched = 0;
// remove the leading slash from the path (to make sure that the uri
// resolution results in a valid path on the dir being checked)
if (pathStr.startsWith("/")) {
pathStr = pathStr.substring(1);
}
Path returnPath = null;
Path path = new Path(pathStr);
if (size == SIZE_UNKNOWN) { // do roulette selection: pick dir with probability
// proportional to available size
long[] availableOnDisk = new long[dirDF.length];
long totalAvailable = 0;
// build the "roulette wheel"
for (int i = 0; i < dirDF.length; ++i) {
availableOnDisk[i] = dirDF[i].getAvailable();
totalAvailable += availableOnDisk[i];
}
// Keep rolling the wheel till we get a valid path
Random r = new java.util.Random();
while (numDirsSearched < numDirs && returnPath == null) {
long randomPosition = Math.abs(r.nextLong()) % totalAvailable;
int dir = 0;
while (randomPosition > availableOnDisk[dir]) {
randomPosition -= availableOnDisk[dir];
dir++;
}
dirNumLastAccessed = dir;
returnPath = createPath(path, checkWrite);
if (returnPath == null) {
totalAvailable -= availableOnDisk[dir];
availableOnDisk[dir] = 0; // skip this disk
numDirsSearched++;
}
}
} else {
while (numDirsSearched < numDirs && returnPath == null) {
long capacity = dirDF[dirNumLastAccessed].getAvailable();
if (capacity > size) {
returnPath = createPath(path, checkWrite);
}
dirNumLastAccessed++;
dirNumLastAccessed = dirNumLastAccessed % numDirs;
numDirsSearched++;
}
}
if (returnPath != null) {
return returnPath;
}
// no path found
throw new DiskErrorException("Could not find any valid local " + "directory for " + pathStr);
}
public void reduce(LongWritable key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
LongWritable curNodeId = key;
double previousPRValue = 1;
double nextPRValue = 0;
double localResidual = 0;
String edgeListOfCurNode = "";
long localResidualTransformed = 0;
for (Text value : values) {
String[] inputInfo = value.toString().split("\\s+");
// incoming pagerank value
if (inputInfo.length == 1) {
nextPRValue += Double.parseDouble(inputInfo[0]);
}
// current node info
else if (inputInfo.length == 3) {
edgeListOfCurNode = inputInfo[2];
previousPRValue = Double.parseDouble(inputInfo[1]);
} else if (inputInfo.length == 2) {
previousPRValue = Double.parseDouble(inputInfo[1]);
} else {
System.out.println("ERROR: received unexpected TEXT in length");
}
}
if (previousPRValue == 1) System.out.println("No node info has been received by a reducer");
// calculate the pagerank value according to the given formula
nextPRValue = pagerankFormula(nextPRValue);
// should also iterate sink nodes list, add the evenly splitted value
// reducer should store the updated node info(NPR) to output directory
context.write(null, new Text(curNodeId + " " + nextPRValue + " " + edgeListOfCurNode));
// then compare PPR with NPR
try {
localResidual = Math.abs(previousPRValue - nextPRValue) / nextPRValue;
localResidualTransformed = (long) (localResidual * 10000);
// System.out.println("Make sure you got the right transformed residual :
// "+localResidualTransformed);
} catch (ArithmeticException e) {
System.out.println("PPR is zero. Check where you get the value!");
}
// assume there is a global counter called residualCounter;
context.getCounter(myCounter.ResidualCounter.RESIDUAL_SUM).increment(localResidualTransformed);
}
public static boolean stopIteration(Configuration conf) throws IOException {
FileSystem fs = FileSystem.get(conf);
Path preFile = new Path("preX/Result");
Path curFile = new Path("curX/part-00000");
if (!(fs.exists(preFile) && fs.exists(curFile))) {
System.exit(1);
}
boolean stop = true;
String line1, line2;
FSDataInputStream in1 = fs.open(preFile);
FSDataInputStream in2 = fs.open(curFile);
InputStreamReader isr1 = new InputStreamReader(in1);
InputStreamReader isr2 = new InputStreamReader(in2);
BufferedReader br1 = new BufferedReader(isr1);
BufferedReader br2 = new BufferedReader(isr2);
while ((line1 = br1.readLine()) != null && (line2 = br2.readLine()) != null) {
String[] str1 = line1.split("\\s+");
String[] str2 = line2.split("\\s+");
double preElem = Double.parseDouble(str1[1]);
double curElem = Double.parseDouble(str2[1]);
if (Math.abs(preElem - curElem) > eps) {
stop = false;
break;
}
}
if (stop == false) {
fs.delete(preFile, true);
if (fs.rename(curFile, preFile) == false) {
System.exit(1);
}
}
return stop;
}
@Override
public int getPartition(IntPair key, NullWritable value, int numPartitions) {
return Math.abs(key.getFirst() * 127) % numPartitions;
}
