float itemAValue = first.getPrefValue();
for (int j = i + 1; j < size; j++) {
ItemPrefWritable second = prefs.get(j);
long itemBID = second.getItemID();
float itemBValue = second.getPrefValue();
output.collect(new ItemItemWritable(itemAID, itemBID), new FloatWritable(itemBValue - itemAValue));
}
}
}