I'm trying to setup a tournament based on votes. Let say user vote for products A, B and C. Each user is presented all possible combinations of products in random order and he picks his preferred product. A user may also dismiss a test in which case each products gets half a point. 

The points of each tests are summed, and divided by the number of users so that we end up with a triangular matrix with a null diagonal and values between 0 and 1. 

How do I deduce a score for each product from this matrix so that I can sort the products in decreasing order of preference ?