/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Reducer#reduce(KEYIN, java.lang.Iterable, org.apache.hadoop.mapreduce.Reducer.Context)
*/
protected void reduce(TextPair key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
sum = count = 0;
for (IntWritable value : values) {
sum += value.get();
++count;
}
avRatingDiff = sum / count;
valueOut.set(key.toString() + fieldDelim + avRatingDiff + fieldDelim + count);
context.write(NullWritable.get(), valueOut);
}
/* (non-Javadoc)
* @see org.apache.hadoop.mapreduce.Mapper#map(KEYIN, VALUEIN, org.apache.hadoop.mapreduce.Mapper.Context)
*/
@Override
protected void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String[] items = value.toString().split(fieldDelim);
String[] ratings = null;
for (int i = 1; i < items.length; ++i) {
ratings = items[i].split(subFieldDelim);
String itemOne = ratings[0];
int ratingOne = Integer.parseInt(ratings[1]);
for (int j = i + 1; j < items.length; ++j) {
ratings = items[i].split(subFieldDelim);
String itemTwo = ratings[0];
int ratingTwo = Integer.parseInt(ratings[1]);
if (itemOne.compareTo(itemTwo) < 0) {
keyOut.set(itemOne, itemTwo);
valOut.set(ratingOne - ratingTwo);
} else {
keyOut.set(itemTwo, itemOne);
valOut.set(ratingTwo - ratingOne);
}
context.write(keyOut, valOut);
}
}
}