CAREER: Cooperative Redundant Threads

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The proposed research enables computers to attain higher speeds, at a time when even slight performance gains are increasingly difficult to achieve by conventional means. The first key discovery is that many instructions specified by a computer program are not strictly required for producing the correct answer. That is, a much shorter program can be constructed that produces the same output in a much shorter period of time. A novel method is proposed for creating a shorter program on-the-fly by completely bypassing parts of the program predicted to be unnecessary. By skipping parts of the program, however, the processor cannot verify that it was alright to do so (because the program has been transformed). The second key discovery is that the full program can be run concurrently with the short program, in order to verify the short program is correct, without noticeably slowing down the short program. The proposed method is called the Slipstream Paradigm, after a technique in auto racing where two cars collaborate aerodynamically to speed up both cars (slipstreaming). Similarly, a slipstream processor finishes two redundant copies of the program sooner that a conventional processor finishes a single copy. Redundant execution is also transparently leveraged for fault tolerance with no additional support. Finally, the Slipstream Paradigm is implementable on emerging multithreaded processors without fundamentally reorganizing their architecture.