Using Graph Properties to Speed-up GPU-based Graph Traversal: A Model-driven Approach

While it is well-known and acknowledged that the performance of graph algorithms is heavily dependent on the input data, there has been surprisingly little research to quantify and predict the impact the graph structure has on performance. Parallel graph algorithms, running on many-core systems such as GPUs, are no exception: most research has focused on how to efficiently implement and tune different graph operations on a specific GPU. However, the performance impact of the input graph has only been taken into account indirectly as a result of the graphs used to benchmark the system. In this work, we present a case study investigating how to use the properties of the input graph to improve the performance of the breadth-first search (BFS) graph traversal. To do so, we first study the performance variation of 15 different BFS implementations across 248 graphs. Using this performance data, we show that significant speed-up can be achieved by combining the best implementation for each level of the traversal. To make use of this data-dependent optimization, we must correctly predict the relative performance of algorithms per graph level, and enable dynamic switching to the optimal algorithm for each level at runtime. We use the collected performance data to train a binary decision tree, to enable high-accuracy predictions and fast switching. We demonstrate empirically that our decision tree is both fast enough to allow dynamic switching between implementations, without noticeable overhead, and accurate enough in its prediction to enable significant BFS speedup. We conclude that our model-driven approach (1) enables BFS to outperform state of the art GPU algorithms, and (2) can be adapted for other BFS variants, other algorithms, or more specific datasets

S+Net: extending functional coordination with extra-functional semantics

This technical report introduces S+Net, a compositional coordination language for streaming networks with extra-functional semantics. Compositionality simplifies the specification of complex parallel and distributed applications; extra-functional semantics allow the application designer to reason about and control resource usage, performance and fault handling. The key feature of S+Net is that functional and extra-functional semantics are defined orthogonally from each other. S+Net can be seen as a simultaneous simplification and extension of the existing coordination language S-Net, that gives control of extra-functional behavior to the S-Net programmer. S+Net can also be seen as a transitional research step between S-Net and AstraKahn, another coordination language currently being designed at the University of Hertfordshire. In contrast with AstraKahn which constitutes a re-design from the ground up, S+Net preserves the basic operational semantics of S-Net and thus provides an incremental introduction of extra-functional control in an existing language.Comment: 34 pages, 11 figures, 3 table

Statistical Performance Analysis of an Ant-Colony Optimisation Application in S-NET

Kenneth MacKenzie, Philip K. F. Hölzenspies, Kevin Hammond, Raimund Kirner, Vu Thien Nga Nguyen, Iraneus te Boekhorst, Clemens Grelck, Raphael Poss, Merijn Verstraaten, 'Statistical Performance Analysis of an Ant-Colony Optimisation Application in S-NET'. Paper presented at the 2nd Workshop on Feedback-Directed Compiler Optimization for Multi-Core Architectures. Berlin, Germany, 12 January 2013.We consider an ant-colony optimsation problem implemented on a multicore system as a collection of asynchronous stream- processing components under the control of the S-NET coordina- tion language. Statistical analysis and visualisation techniques are used to study the behaviour of the application, and this enables us to discover and correct problems in both the application program and the run-time system underlying S-NET

A sampling-based tool for scaling graph datasets

Graph processing has become a topic of interest in many domains. However, we still observe a lack of representative datasets for in-depth performance and scalability analysis. Neither data collections, nor graph generators provide enough diversity and control for thorough analysis. To address this problem, we proposea heuristic method for scaling existing graphs. Our approach, based onsampling andinterconnection, can provide a scaled "version" of a given graph. Moreover, we provide analytical models to predict the topological properties of the scaled graphs (such as the diameter, degree distribution, density, or the clustering coefficient), and further enable the user to tweak these properties. Property control is achieved through a portfolio of graph interconnection methods (e.g., star, ring, chain, fully connected) applied for combining the graph samples. We further implement our method as an open-source tool which can be used to quickly provide families of datasets for in-depth benchmarking of graph processing algorithms. Our empirical evaluation demonstrates our tool provides scaled graphs of a wide range of sizes, whose properties match well with model predictions and/or user requirements. Finally, we also illustrate, through a case-study, how scaled graphs can be used for in-depth performance analysis of graph processing algorithms

OMUSE

The Oceanographic Multi-purpose Software Environment: a package for multi-physics and multi-scale earth science simulations

UvA-DARE (Digital Academic Repository) Task Migration for S-Net/LPEL FD-COMA 2013 2nd HiPEAC Workshop on Feedback-Directed Compiler Optimization for Multicore Architectures Task Migration for S-Net/LPEL

Abstract We propose an extension to S-NET's light-weight parallel execution layer (LPEL): dynamic migration of tasks between cores for improved load balancing and higher throughput of S-NET streaming networks. We sketch out the necessary implementation steps and empirically analyse the impact of task migration on a variety of S-NET applications

OMUSE

The Oceanographic Multi-purpose Software Environment: a package for multi-physics and multi-scale earth science simulations