question: public void reduce ( FloatWritable key , Iterator < Text > values , OutputCollector < Text , FloatWritable > output , Reporter reporter ) throws IOException { float val = key . get ( ) ; FloatWritable number = new FloatWritable ( val == 0 ? 0 : - val ) ; long numCollected = 0 ; while ( values . hasNext ( ) && ( numCollected < topn ) ) { Text url = WritableUtils . clone ( values . next ( ) , conf ) ; output . collect ( url , number ) ; numCollected ++ ; } }
target:  Flips and collects the url and numeric sort value.