title: How to evaluate quality of link prediction task?
body: <p>I understand that here we can use precision, recall, AUC,  etc. I mean this: we have 4 users ('a', 'b', 'c', 'd') and we have got prediction that user 'a' will have link with 'b' with probability 0.7, with 'c' 0.4, and with 'd' 0.3, but really user 'a' added to friend list only  user 'c', so how to evaluate accuracy of our predictions?</p>