John Snodgrass writes: "Neil Hunt, Chief Product Officer at Netflix, has announced on the Netflix Prize Forums that they are planning to hold a new data mining competition. The second competition will have some twists and is expected to be shorter in duration. It will feature two grand prizes, to be awarded in a 6 and 18 month time frame. A previous competitor still active on the board has already dubbed it: The Sparse Matrix: Reordered" and "The Sparse Matrix: Factorizations"."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"