Abstract
In particle transport simulations, radiation effects are often described by the discrete ordinates (S n ) form of Boltzmann equation. In each ordinate direction, the solution is computed by sweeping the radiation flux across the grid. Parallel S n sweep on an unstructured grid can be explicitly modeled as topological traversal through an equivalent directed acyclic graph (DAG), which is a data-driven algorithm. Its traditional design using MPI model results in irregular communication of massive short messages which cannot be efficiently handled by MPI runtime. Meanwhile, in high-end HPC cluster systems, multicore has become the standard processor configuration of a single node. The traditional data-driven algorithm of S n sweeps has not exploited potential advantages of multi-threading of multicore on shared memory. These advantages, however, as we shall demonstrate, could provide an elegant solution resolving problems in the previous MPI-only design. In this paper, we give a new design of data-driven parallel S n sweeps using hybrid MPI and Pthread programming, namely Sweep-H, to exploit hierarchical parallelism of processes and threads. With special multi-threading techniques and vertex schedule policy, Sweep-H gets more efficient communication and better load balance. We further present an analytical performance model for Sweep-H to reveal why and when it is advantageous over former MPI counterpart. On a 64-node multicore cluster system with 12 cores per node, 768 cores in total, Sweep-H achieves nearly linear scalability for moderate problem sizes, and better absolute performance than the previous MPI algorithm on more than 16 nodes (by up to two times speedup on 64 nodes).
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Downar T, Siegel A, Unal C. Science based nuclear energy systems enabled by advanced modeling and simulation at the extreme scale. Report of Workshop on Nuclear Energy, May 2009, http://science.energy.gov/~/media/ascr/pdf/programdocuments/docs/Sc_nework_shop_report.pdf.
Baker R S, Alcouffe R E. Parallel 3-D Sn performance for MPI on cray-T3D. In Proc. Joint Int. Conf. Math. Methods and Supercomputing for Nuclear Applicat., Oct. 1997, pp.377-393.
Baker R S, Koch K R. An Sn algorithm for the massively parallel CM-200 computer. Nuclear Science and Engineering, 1998, 28: 312–320.
Valiant L G. A bridging model for parallel computation. Communications of the ACM, 1990, 33(8): 103–111.
Plimpton S, Hendrickson B, Burns S et al. Parallel algorithms for radiation transport on unstructured grids. In Proc. ACM/IEEE Conf. Super Computing, Nov. 2000, Article No.25.
Plimpton S, Hendrickson B, Burns S et al. Parallel S n sweeps on unstructured grids: Algorithms for prioritization, grid partitioning, and cycle detection. J. American Nuclear Science and Engineering, 2005, 150(3): 267–283.
Mo Z Y, Zhang A Q, Cao X L. Towards a parallel framework of grid-based numerical algorithms on DAGs. In Proc. the 20th IPDPS, Apr. 2006, p.310.
Hewitt C, Bishop P, Steiger R. A universal modular actor formalism for artificial intelligence. In Proc. the 3rd IJCAI, Aug. 1973, pp.235-245.
Schloegel K, Karypis G, Kumar V. Parallel static and dynamic multi-constraint graph partitioning. Concurrency and Computation: Practice and Experience, 2002, 14(3): 219–240.
Karypis G, Kumar V. Multi-level graph partitioning schemes. In Proc. ICPP, Aug. 1995, pp.113-122.
Hendrickson B, Leland R. A multilevel algorithm for partitioning graph. In Proc. ACM/IEEE Conf. Super Computing, Dec. 1995, Article No.28.
Zhang A Q. Research on scalable parallel data driven algorithms and applications [Ph.D. Thesis]. China Academy of Engineering Physics, 2009.
Pautz S D. An algorithm for parallel S n sweeps on unstructured meshes. Nuclear Science and Engineering, 2002, 140(2): 111–136.
Nowak P, Nemanic M K. Radiation transport calculations on unstructured grids using a spatially decomposed and threaded algorithm. In Proc. Int. Conf. Mathematics and Computation, Reactor Physics and Environmental Analysis in Nuclear Applications, Sept. 1999, pp.379-390.
Gong C Y, Liu J, Chi L H, Huang H W, Fang J Y, Gong Z H. GPU accelerated simulations of 3D deterministic particle transport using discrete ordinates method. Journal of Computational Physics, 2011, 230(15): 6010–6022.
Lubeck O, Lang M, Srinivasan R, Johnson G. Implementation and performance modeling of deterministic particle transport (Sweep3D) on the IBM Cell/BE. Scientific Programming, 2009, 17(1/2): 199–208.
Pennycook S J, Hammond S D, Mudalige G R, Wright S A, Jarvis S A. On the acceleration of wavefront applications using distributed many-core architectures. The Computer Journal, 2012, 55(2): 138–153.
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This work is supported by the National Natural Science Foundation of China under Grant Nos. 60925009, 61003062, 61033009, 61272134, and the National Basic 973 Program of China under Grant Nos. 2011CB302502 and 2012CB316502.
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Yan, J., Tan, GM. & Sun, NH. Optimizing Parallel S n Sweeps on Unstructured Grids for Multi-Core Clusters. J. Comput. Sci. Technol. 28, 657–670 (2013). https://doi.org/10.1007/s11390-013-1366-9
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DOI: https://doi.org/10.1007/s11390-013-1366-9