In this task, you are given a part of an article. Your task is to generate headline (title) for this text. Preferred headlines are under fifteen words.

Recommender systems play an increasingly important role in online applications to help users find what they need or prefer. Collaborative filtering algorithms that generate predictions by analyzing the user-item rating matrix perform poorly when the matrix is sparse. To alleviate this problem, this paper proposes a simple recommendation algorithm that fully exploits the similarity information among users and items and intrinsic structural information of the user-item matrix. The proposed method constructs a new representation which preserves affinity and structure information in the user-item rating matrix and then performs recommendation task. To capture proximity information about users and items, two graphs are constructed. Manifold learning idea is used to constrain the new representation to be smooth on these graphs, so as to enforce users and item proximities. Our model is formulated as a convex optimization problem, for which we need to solve the well known Sylvester equation only. We carry out extensive empirical evaluations on six benchmark datasets to show the effectiveness of this approach.
Top-N Recommendation on Graphs

We introduce a new spatial data structure for high dimensional data called the approximate principal direction tree (APD tree) that adapts to the intrinsic dimension of the data. Our algorithm ensures vector-quantization accuracy similar to that of computationally-expensive PCA trees with similar time-complexity to that of loweraccuracy RP trees. APD trees use a small number of powermethod iterations to find splitting planes for recursively partitioning the data. As such they provide a natural trade-off between the running-time and accuracy achieved by RP and PCA trees. Our theoretical results establish a) strong performance guarantees regardless of the convergence rate of the powermethod and b) that O(log d) iterations suffice to establish the guarantee of PCA trees when the intrinsic dimension is d. We demonstrate this trade-off and the efficacy of our data structure on both the CPU and GPU.
Approximate Principal Direction Trees

To improve user satisfaction, mobile app developers are interested in relevant user opinions such as complaints or suggestions. An important source for such opinions is user reviews on online app markets. However, manual review analysis for useful opinions is often challenging due to the large amount and the noisy-nature of user reviews. To address this problem, we propose M.A.R.K, a keyword-based framework for semiautomated review analysis. The key task of M.A.R.K is to analyze reviews for keywords of potential interest which developers can use to search for useful opinions. We have developed several techniques for that task including: 1) keyword extracting with customized regularization algorithms; 2) keyword grouping with distributed representation; and 3) keyword ranking with ratings and frequencies analysis. Our empirical evaluation and case studies show that M.A.R.K can identify keywords of high interest and provide developers with useful user opinions. KeywordsApp Review, Opinion Mining, Keyword
Mining User Opinions in Mobile App Reviews: A Keyword-based Approach