Music recommendation systems based on Collaborative Filtering methods have been extensively developed over the last years. Typically, they work by analyzing the past usersong relationships, and provide informed guesses based on the overall information collected from other users. Although the music listening behavior is a repetitive and time-dependent process, these methods have not taken this into account and only consider user-song interaction for recommendation. In this work, we explore the usage of temporal context and session diversity in Session-based Collaborative Filtering techniques for music recommendation. We compared two techniques to capture the users' listening patterns over time: one explicitly extracts temporal properties and session diversity, to group and compare the similarity of sessions; the other uses a generative topic modeling algorithm, which is able to implicitly model temporal patterns. We evaluated the developed algorithms by measuring the Hit Ratio, and the Mean Reciprocal Rank. Results reveal that the inclusion of temporal information, either explicitly or implicitly, increases significantly the accuracy of the recommendation, while compared to the traditional session-based CF.

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Transactional memory systems providing snapshot isolation enable concurrent access to shared data without incurring aborts on read-write conflicts. Reducing aborts is extremely relevant as it leads to higher concurrency, greater performance, and better predictability. Unfortunately, snapshot isolation does not provide serializability as it allows certain anomalies that can lead to subtle consistency violations. While some mechanisms have been proposed to verify the correctness of a program utilizing snapshot isolation transactions, it remains difficult to repair incorrect applications. To reduce the programmer's burden in this case, we present a technique based on dynamic code and graph dependency analysis that automatically corrects existing snapshot isolation anomalies in transactional memory programs. Our evaluation shows that corrected applications retain the performance benefits characteristic of snapshot isolation over conventional transactional memory systems.