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2004 International Conference on Parallel Processing (ICPP'04)
Non-Uniform Dependences Partitioned by Recurrence Chains
Montreal, Quebec, Canada
August 15-August 18
ISBN: 0-7695-2197-5
Yijun Yu, University of Toronto
Erik H. D?Hollander, Ghent University
Non-uniform distance loop dependences are a known obstacle to find parallel iterations. To find the outermost loop parallelism in these "irregular" loops, a novel method is presented based on recurrence chains. The scheme organizes non-uniformly dependent iterations into lexicographically ordered monotonic chains. While the initial and final iterations of monotonic chains form two parallel sets, the remaining iterations form an intermediate set that can be partitioned further. When there is only one pair of coupled array references, the non-uniform dependences are represented by a single recurrence equation. In that case, the chains in the intermediate set do not bifurcate and each can be executed as a WHILE loop. The independent and the initial iterations of monotonic dependence chains constitute the outermost parallelism. The proposed approach compares favorably with other treatments of non-uniform dependences in the literature. When there are multiple recurrence equations, a dataflow parallel execution can be scheduled using the technique to find maximum loop parallelism.
Index Terms:
non-uniform dependences, loop parallelization, recurrence chains, iteration space partitioning, imperfectly nested loop
Citation:
Yijun Yu, Erik H. D?Hollander, "Non-Uniform Dependences Partitioned by Recurrence Chains," icpp, pp.100-107, 2004 International Conference on Parallel Processing (ICPP'04), 2004
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