Multi-GPU Graph Analytics

We present a single-node, multi-GPU programmable graph processing library that allows programmers to easily extend single-GPU graph algorithms to achieve scalable performance on large graphs with billions of edges. Directly using the single-GPU implementations, our design only requires programmers to specify a few algorithm-dependent concerns, hiding most multi-GPU related implementation details. We analyze the theoretical and practical limits to scalability in the context of varying graph primitives and datasets. We describe several optimizations, such as direction optimizing traversal, and a just-enough memory allocation scheme, for better performance and smaller memory consumption. Compared to previous work, we achieve best-of-class performance across operations and datasets, including excellent strong and weak scalability on most primitives as we increase the number of GPUs in the system.Comment: 12 pages. Final version submitted to IPDPS 201

Gunrock: GPU Graph Analytics

For large-scale graph analytics on the GPU, the irregularity of data access and control flow, and the complexity of programming GPUs, have presented two significant challenges to developing a programmable high-performance graph library. "Gunrock", our graph-processing system designed specifically for the GPU, uses a high-level, bulk-synchronous, data-centric abstraction focused on operations on a vertex or edge frontier. Gunrock achieves a balance between performance and expressiveness by coupling high performance GPU computing primitives and optimization strategies with a high-level programming model that allows programmers to quickly develop new graph primitives with small code size and minimal GPU programming knowledge. We characterize the performance of various optimization strategies and evaluate Gunrock's overall performance on different GPU architectures on a wide range of graph primitives that span from traversal-based algorithms and ranking algorithms, to triangle counting and bipartite-graph-based algorithms. The results show that on a single GPU, Gunrock has on average at least an order of magnitude speedup over Boost and PowerGraph, comparable performance to the fastest GPU hardwired primitives and CPU shared-memory graph libraries such as Ligra and Galois, and better performance than any other GPU high-level graph library.Comment: 52 pages, invited paper to ACM Transactions on Parallel Computing (TOPC), an extended version of PPoPP'16 paper "Gunrock: A High-Performance Graph Processing Library on the GPU

Performance Characterization of High-Level Programming Models for GPU Graph Analytics

We identify several factors that are critical to high-performance GPU graph analytics: efficient building block operators, synchronization and data movement, workload distribution and load balancing, and memory access patterns. We analyze the impact of these critical factors through three GPU graph analytic frameworks, Gunrock, MapGraph, and VertexAPI2. We also examine their effect on different workloads: four common graph primitives from multiple graph application domains, evaluated through real-world and synthetic graphs. We show that efficient building block operators enable more powerful operations for fast information propagation and result in fewer device kernel invocations, less data movement, and fewer global synchronizations, and thus are key focus areas for efficient large-scale graph analytics on the GPU

Preparation of water-soluble multi-walled carbon nanotubes by Ce(IV)-induced redox radical polymerization

Abstract Poly(acrylic acid), poly(N-isopropylacrylamide) and polyacrylamide functionalized MWNTs were prepared by Ce(IV)-induced redox radical polymerization. The reaction can be conducted in aqueous media at room temperature, and the polymer graft ratio increased with the increase of monomer feed ratio. MWNTs anchored with PAA on the surface are pH sensitive and exhibit a reversible assembly-deassembly response in aqueous solution, whereas those coated with PNIPAM are thermally sensitive. All the polymer-functionalized MWNTs are highly soluble in water to give robust stable black solutions. Such water-soluble MWNTs are promising for biological and biomedical applications

Effect of Re on microstructure and mechanical properties of γ/γʹ Co-Ti-based superalloys

Abstract(#br)Three compositions of Re containing Co-Ti-based alloys with γ/γ′ two-phase microstructure were obtained based on the determined phase relationship in the Co-rich corner at 800 °C. The effect of Re on microstructure, elemental partition behavior, thermodynamic properties, lattice parameter misfits, mechanical properties and γ′ coarsening behavior of the Co-Ti-Re alloys were investigated. The γ/γ′ lattice parameter misfit of the alloys decreases from 0.72% to 0.50%, and the γ′ coarsening rate constant K of alloys decreases from 0.30 × 10 −27 m 3 s −1 to 0.073 × 10 −27 m 3 s −1 as Re content increasing form 1 at. % to 5 at. %. Additionally, the volume fraction of γ′ phase (V γ′ ) increases from 42.15% to 53.19% and the γ′ solvus temperature increases from 1059 °C to 1085 °C ( T solvus-γ′ ) with increasing Re content. Moreover, the 0.2% flow stresses and the 0.2% specific flow stresses of all three alloys exhibit negative temperature dependence at the temperatures ranging from room temperature to 900 °C. And both the 0.2% flow stresses and the 0.2% specific flow stresses increase with the Re content

Experimental Investigation of Diagram Equilibria in the Co-Nb-Re Ternary System

Abstract(#br)In this study, the isothermal sections of the Co-Nb-Re ternary system at 1200, and 1300 °C have been experimentally determined combining the means of electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The obtained experimental results showed that: (1) The Laves phase of λ3-Co2Nb (C36) was stable at 1300 °C. The temperature was beyond its stability limit in Co-Nb binary system. (2) The solubility of Re in the λ3 phase was so large that the nearest λ2-Co2Nb (C15) phase was essentially surrounded. (3) The solubility of Re in the μ-Co7Nb6 phase was 34.0 at.% at 1200 °C and 35.2 at.% at 1300 °C, respectively. (4) The liquid phase existed at 1300 °C dissolving about 4.0 at.% Re, but it was..