Implement the PageRank algorithm with Mapper-Reducer
hdfs dfs -rm -r /transition # remove /transition dir in HDFS，if it not exists，ignore the error info.
hdfs dfs -mkdir /transition # create /transition dir in HDFS
hdfs dfs -put transition.txt /transition # copy the transisiton.txt to hdfs /transition
hdfs dfs -rm -r /output* # remove /output dir，if it not exists，ignore the error info.
hdfs dfs -rm -r /pagerank* # remove /pagerank dir
hdfs dfs -mkdir /pagerank0 # create /pagerank0 dir
hdfs dfs -put prsmall.txt /pagerank0 #upload PR0
hadoop com.sun.tools.javac.Main *.java # compile java source code
jar cf pr.jar *.class # jar all the compiled class files
hadoop jar pr.jar Driver /transition /pagerank /output 1 #run jar
//args0: dir of transition.txt
//args1: dir of PageRank.txt
//args2: dir of unitMultiplication result
//args3: times of convergence（make sure the code run successfully when args3=1, then test args3=40）