PageRank implemented by mapreduce

Input Format:
A 1 B, c, d
B 1 c, d
Map:
B A 1/3
A 1/3
D A 1/3
A | B, c, d
C B 1/2
D B 1/2
B | c, d
Reduce:
B (1-0.85) + 0.85*1/3 c, d
  
C (1-0.85) + 0.85*5/6

D (1-0.85) + 0.85*5/6
A (1-0.85) + 0.85*1 B, c, d


Import Java. io. ioexception; import Org. apache. hadoop. conf. configuration; import Org. apache. hadoop. FS. path; import Org. apache. hadoop. io. longwritable; import Org. apache. hadoop. io. text; import Org. apache. hadoop. mapreduce. job; import Org. apache. hadoop. mapreduce. mapper; import Org. apache. hadoop. mapreduce. reducer; import Org. apache. hadoop. mapreduce. lib. input. fileinputformat; import Org. apache. hadoop. mapreduce. lib. output. fileoutputformat; public class pagerankiter {Private Static final double damping = 0.85; public static class pritermapper extends mapper <longwritable, text> {public void map (longwritable key, text value, context context) throws ioexception, interruptedexception {string line = value. tostring (); string [] tuple = line. split ("\ t"); string pagekey = tuple [0]; double pr = double. parsedouble (tuple [1]); If (tuple. length> 2) {string [] linkpages = tuple [2]. split (","); For (string linkpage: linkpages) {string prvalue = pagekey + "\ t" + String. valueof (Pr/linkpages. length); context. write (new text (linkpage), new text (prvalue);} context. write (new text (pagekey), new text ("|" + tuple [2]) ;}} public static class priterreducer extends reducer <text, text> {public void reduce (Text key, iterable <text> values, context) throws ioexception, interruptedexception {string links = ""; double PageRank = 0; For (text value: values) {string TMP = value. tostring (); If (TMP. startswith ("|") {links = "\ t" + TMP. substring (TMP. indexof ("|") + 1); // index starts from 0 to continue;} string [] tuple = TMP. split ("\ t"); If (tuple. length> 1) PageRank + = double. parsedouble (tuple [1]);} PageRank = (double) (1-damping) + damping * PageRank; // The iteration formula context of PageRank. write (new text (key), new text (string. valueof (PageRank) + Links);} public static void main (string [] ARGs) throws exception {configuration conf = new configuration (); job job2 = new job (Conf, "pagerankiter"); job2.setjarbyclass (pagerankiter. class); job2.setoutputkeyclass (text. class); job2.setoutputvalueclass (text. class); job2.setmapperclass (pritermapper. class); job2.setreducerclass (priterreducer. class); fileinputformat. addinputpath (job2, New Path (ARGs [0]); fileoutputformat. setoutputpath (job2, New Path (ARGs [1]); job2.waitforcompletion (true );}}

Input is the output above
Input Format:
A PR
B PR
...

Import Java. io. ioexception; import Org. apache. hadoop. conf. configuration; import Org. apache. hadoop. FS. path; import Org. apache. hadoop. io. longwritable; import Org. apache. hadoop. io. floatwritable; import Org. apache. hadoop. io. writablecomparable; import Org. apache. hadoop. io. writablecomparator; import Org. apache. hadoop. io. text; import Org. apache. hadoop. mapreduce. job; import Org. apache. hadoop. mapreduce. mapper; import Org. apache. hadoop. mapreduce. lib. input. fileinputformat; import Org. apache. hadoop. mapreduce. lib. output. fileoutputformat; public class pagerankviewer {public static class pagerankviewermapper extends mapper <longwritable, text, floatwritable, text> {private text outpage = new text (); Private floatwritable outpr = new floatwritable (); public void map (longwritable key, text value, context) throws ioexception, interruptedexception {string [] line = value. tostring (). split ("\ t"); string page = line [0]; float Pr = float. parsefloat (line [1]); outpage. set (PAGE); outpr. set (PR); context. write (outpr, outpage) ;}/ ** reload the key comparison function so that it goes through shuffle and sort in reverse order (from large to small) output **/public static class descfloatcomparator extends floatwritable. comparator {// @ override public float compare (writablecomparator A, writablecomparable <floatwritable> B) {return-Super. compare (a, B);} public int compare (byte [] B1, int S1, int L1, byte [] B2, int S2, int l2) {return-Super. compare (B1, S1, L1, B2, S2, L2) ;}} public static void main (string [] ARGs) throws exception {configuration conf = new configuration (); job job3 = new job (Conf, "pagerankviewer"); job3.setjarbyclass (pagerankviewer. class); job3.setoutputkeyclass (floatwritable. class); job3.setsortcomparatorclass (descfloatcomparator. class); job3.setoutputvalueclass (text. class); job3.setmapperclass (pagerankviewermapper. class); fileinputformat. addinputpath (job3, New Path (ARGs [0]); fileoutputformat. setoutputpath (job3, New Path (ARGs [1]); job3.waitforcompletion (true );}}

　　

PageRank implemented by mapreduce