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  1. There are nearly one hundred parallel and distributed graph processing packages. Selecting the best package for a given problem is difficult; some packages require GPUs, some are optimized for distributed or shared memory, and some require proprietary compilers or perform better on different hardware. Furthermore, performance may vary wildly depending on the graph itself. This complexity makes selecting the optimal implementation manually infeasible. We develop an approach to predict the performance of parallel graph processing using both regression models and binary classification by labeling configurations as either well-performing or not. We demonstrate our approach on six graph processing packages: GraphMat,more »the Graph500, the Graph Algorithm Platform Benchmark Suite, GraphBIG, Galois, and PowerGraph and on four algorithms: PageRank, single-source shortest paths, triangle counting, and breadth first search. Given a graph, our method can estimate execution time or suggest an implementation and thread count expected to perform well. Our method correctly identifies well-performing configurations in 97% of test cases.« less
  2. Doglioni, C. ; Kim, D. ; Stewart, G.A. ; Silvestris, L. ; Jackson, P. ; Kamleh, W. (Ed.)
    One of the most computationally challenging problems expected for the High-Luminosity Large Hadron Collider (HL-LHC) is finding and fitting particle tracks during event reconstruction. Algorithms used at the LHC today rely on Kalman filtering, which builds physical trajectories incrementally while incorporating material effects and error estimation. Recognizing the need for faster computational throughput, we have adapted Kalman-filterbased methods for highly parallel, many-core SIMD and SIMT architectures that are now prevalent in high-performance hardware. Previously we observed significant parallel speedups, with physics performance comparable to CMS standard tracking, on Intel Xeon, Intel Xeon Phi, and (to a limited extent) NVIDIA GPUs.more »While early tests were based on artificial events occurring inside an idealized barrel detector, we showed subsequently that our mkFit software builds tracks successfully from complex simulated events (including detector pileup) occurring inside a geometrically accurate representation of the CMS-2017 tracker. Here, we report on advances in both the computational and physics performance of mkFit, as well as progress toward integration with CMS production software. Recently we have improved the overall efficiency of the algorithm by preserving short track candidates at a relatively early stage rather than attempting to extend them over many layers. Moreover, mkFit formerly produced an excess of duplicate tracks; these are now explicitly removed in an additional processing step. We demonstrate that with these enhancements, mkFit becomes a suitable choice for the first iteration of CMS tracking, and eventually for later iterations as well. We plan to test this capability in the CMS High Level Trigger during Run 3 of the LHC, with an ultimate goal of using it in both the CMS HLT and offline reconstruction for the HL-LHC CMS tracker.« less
  3. Computing the single-source shortest path (SSSP) is one of the fundamental graph algorithms, and is used in many applications. Here, we focus on computing SSSP on large dynamic graphs, i.e. graphs whose structure evolves with time. We posit that instead of recomputing the SSSP for each set of changes on the dynamic graphs, it is more efficient to update the results based only on the region of change. To this end, we present a novel two-step shared-memory algorithm for updating SSSP on weighted large-scale graphs. The key idea of our algorithm is to identify changes, such as vertex/edge addition andmore »deletion, that affect the shortest path computations and update only the parts of the graphs affected by the change. We provide the proof of correctness of our proposed algorithm. Our experiments on real and synthetic networks demonstrate that our algorithm is as much as 4X faster compared to computing SSSP with Galois, a state-of-the-art parallel graph analysis software for shared memory architectures. We also demonstrate how increasing the asynchrony can lead to even faster updates. To the best of our knowledge, this is one of the first practical parallel algorithms for updating networks on shared-memory systems, that is also scalable to large networks.« less
  4. Computing single-source shortest paths (SSSP) is one of the fundamental problems in graph theory. There are many applications of SSSP including finding routes in GPS systems and finding high centrality vertices for effective vaccination. In this paper, we focus on calculating SSSP on big dynamic graphs, which change with time. We propose a novel distributed computing approach, SSSPIncJoint, to update SSSP on big dynamic graphs using GraphX. Our approach considerably speeds up the recomputation of the SSSP tree by reducing the number of map-reduce operations required for implementing SSSP in the gather-apply- scatter programming model used by GraphX.
  5. In this paper, we present a network-based template for analyzing large-scale dynamic data. Specifically, we present a novel shared-memory parallel algorithm for updating treebased structures, including connected components (CC) and the minimum spanning tree (MST) on dynamic networks. We propose a rooted tree-based data structure to store the edges that are most relevant to the analysis. Our algorithm is based on updating the information stored in this rooted tree.In this paper, we present a network-based template for analyzing large-scale dynamic data. Specifically, we present a novel shared-memory parallel algorithm for updating tree-based structures, including connected components (CC) and the minimummore »spanning tree (MST) on dynamic networks. We propose a rooted tree-based data structure to store the edges that are most relevant to the analysis. Our algorithm is based on updating the information stored in this rooted tree.« less