[Spark][Python]PageRank 程序

PageRank 程序：

file contents:

page1 page3
page2 page1
page4 page1
page3 page1
page4 page2
page3 page4

def computeContribs(neighbors,rank):
    for neighbor in neighbors: yield( neighbor, rank/len(neighbors) )

links = sc.textFile("tst001.txt").map(lambda line: line.split()).map(lambda pages: (pages[0],pages[1]))\
.distinct().groupByKey().persist()

ranks=links.map(lambda (page,neighbors): (page,1.0) )

In [4]: for x in range(1):
...: print "links count:"+links.count()
...: print "ranks count:" ranks.count()

In [11]: for x in range(3):
....: contribs=links.join(ranks).flatMap( lambda (page,(neighbors,rank)): computeContribs(neighbors,rank) )
....: ranks=contribs.reduceByKey(lambda v1,v2: v1+v2).map(lambda (page,contrib): (page,contrib*0.85+0.15))
....:

for rank in ranks.collect(): print rank

(u'page2', 0.394375)
(u'page3', 1.2619062499999998)
(u'page4', 0.8820624999999999)
(u'page1', 1.4616562499999997)