Network Flow Based Post Processing for Sales Diversity

TL;DR

This paper introduces a network flow-based post-processing method to enhance diversity in collaborative filtering recommendation systems, balancing diversity with rating quality effectively.

Contribution

It formulates recommendation diversity as a subgraph selection problem and develops a fast network flow algorithm to optimize this diversity measure.

Findings

Increased recommendation diversity on Netflix and MovieLens datasets.

Maintained high rating quality while improving diversity.

Proposed a flexible diversity model with prescribed recommendation distributions.

Abstract

Collaborative filtering is a broad and powerful framework for building recommendation systems that has seen widespread adoption. Over the past decade, the propensity of such systems for favoring popular products and thus creating echo chambers have been observed. This has given rise to an active area of research that seeks to diversify recommendations generated by such algorithms. We address the problem of increasing diversity in recommendation systems that are based on collaborative filtering that use past ratings to predicting a rating quality for potential recommendations. Following our earlier work, we formulate recommendation system design as a subgraph selection problem from a candidate super-graph of potential recommendations where both diversity and rating quality are explicitly optimized: (1) On the modeling side, we define a new flexible notion of diversity that allows a system designer to prescribe the number of recommendations each item should receive, and smoothly penalizes deviations from this distribution. (2) On the algorithmic side, we show that minimum-cost network flow methods yield fast algorithms in theory and practice for designing recommendation subgraphs that optimize this notion of diversity. (3) On the empirical side, we show the effectiveness of our new model and method to increase diversity while maintaining high rating quality in standard rating data sets from Netflix and MovieLens.