David I. August
Professor in the Department of Computer Science, Princeton University
Affiliated with the Department of Electrical Engineering, Princeton University
Ph.D. May 2000, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign

Office: Computer Science Building Room 221
Email: august@princeton.edu
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Fax: (609) 964-1699
Administrative Assistant: Pamela DelOrefice, (609) 258-5551

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Speculatively Exploiting Cross-Invocation Parallelism [abstract] (PDF)
Jialu Huang, Prakash Prabhu, Thomas B. Jablin, Soumyadeep Ghosh, Sotiris Apostolakis, Jae W. Lee, and David I. August
Proceedings of the 25th International Conference on Parallel Architectures and Compilation Techniques (PACT), September 2016.
Accept Rate: 26% (31/119).

Automatic parallelization has shown promise in producing scalable multi-threaded programs for multi-core architectures. Most existing automatic techniques parallelize independent loops and insert global synchronization between loop invocations. For programs with many loop invocations, frequent synchronization often becomes the performance bottleneck. Some techniques exploit cross-invocation parallelism to overcome this problem. Using static analysis, they partition iterations among threads to avoid cross-thread dependences. However, this approach may fail if dependence pattern information is not available at compile time. To address this limitation, this work proposes SpecCross-–the first automatic parallelization technique to exploit cross-invocation parallelism using speculation. With speculation, iterations from different loop invocations can execute concurrently, and the program synchronizes only on misspeculation. This allows SpecCross to adapt to dependence patterns that only manifest on particular inputs at runtime. Evaluation on eight programs shows that SpecCross achieves a geomean speedup of 3.43× over parallel execution without cross-invocation parallelization.