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Wasp: Efficient Asynchronous Single-Source Shortest Path on Multicore Systems via Work Stealing
DescriptionThe Single-Source Shortest Path (SSSP) problem is a fundamental graph problem with an extensive set of real-world applications. State-of-the-art parallel algorithms for SSSP, such as the ∆-stepping algorithm, create parallelism through priority coarsening. Priority coarsening results in redundant computations that diminish the benefits of parallelization and limit parallel scalability.

This paper introduces Wasp, a novel SSSP algorithm that reduces parallelism-induced redundant work by utilizing asynchrony and an efficient priority-aware work stealing scheme. Contrary to previous work, Wasp introduces redundant computations only when threads have no high-priority work locally available to execute. This is achieved by a novel priority-aware work stealing mechanism that controls the inefficiencies of indiscriminate priority coarsening.

Experimental evaluation shows competitive or better performance compared to GAP, GBBS, MultiQueues, Galois, ∆*-stepping, and ρ-stepping on 13 diverse graphs with geometric mean speedups of 2.26x on AMD Zen 3 and 2.16x on Intel Sapphire Rapids using 128 threads.