the similarity matrix is symmetrical. This simply means that if user A is similarity to user B with a similarity value X then user B will be similar to user A with a similarity value equal to X. (查看原文)
Bell and Keorren are leading the Netflix prize competitioin (at the time of this writing), and their assessment was the following: "we found no perfect models. Instead, our best results came from combining predictions of models that complemented each other." (查看原文)
