Electrical & Computer Engineering Research Works

Permanent URI for this collectionhttp://hdl.handle.net/1903/1658

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Author: search.filters.author.Pari, Pushkin R.

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    Dual-Processor Design of Energy Efficient Fault-Tolerant System
    (IEEE, 2006-09) Hua, Shaoxiong; Pari, Pushkin R.; Qu, Gang
    A popular approach to guarantee fault tolerance in safety-critical applications is to run the application on two processors. A checkpoint is inserted at the comple- tion of the primary copy. If there is no fault, the sec- ondary processor terminates its execution. Otherwise, should the fault occur, the second processor continues and completes the application before its deadline. In this paper, we study the energy efficiency of such dual- processor system. Specifically, we first derive an opti- mal static voltage scaling policy for single periodic task. We then extend it to multiple periodic tasks based on worst case execution time (WCET) analysis. Finally, we discuss how to further reduce system’s energy con- sumption at run time by taking advantage of the actual execution time which is less than the WCET. Simula- tion on real-life benchmark applications shows that our technique can save up to 80% energy while still provid- ing fault tolerance.
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    How Many Solutions Does a SAT Instance Have?
    (IEEE, 2004-05) Pari, Pushkin R.; Yuan, Lin; Qu, Gang
    Our goal is to investigate the solution space of a given Boolean Satisfiability (SAT) instance. In particular, we are interested in determining the size of the solution space – the number of truth assignments that make the SAT instance true – and finding all such truth assignments, if possible. This apparently hard problem has both theoretical and practical values. We propose an exact algorithm based on exhaustive search that Solves the instance Once and Finds All Solutions (SOFAS) and several sampling techniques that estimate the size of the solution space. SOFAS works better for SAT instances of small size with a 5X-100X speed-up over the brute force search algorithm. The sampling techniques estimate the solution space reasonably well for standard SAT benchmarks.