Anne E. Trefethen

The International Exascale Software Project roadmap

Over the last 20 years, the open-source community has provided more and more software on which the world’s high-performance computing systems depend for performance and productivity. The community has invested millions of dollars and years of effort to build key components. However, although the investments in these separate software elements have been tremendously valuable, a great deal of productivity has also been lost because of the lack of planning, coordination, and key integration of technologies necessary to make them work together smoothly and efficiently, both within individual petascale systems and between different systems. It seems clear that this completely uncoordinated development model will not provide the software needed to support the unprecedented parallelism required for peta/ exascale computation on millions of cores, or the flexibility required to exploit new hardware models and features, such as transactional memory, speculative execution, and graphics processing units. This report describes the work of the community to prepare for the challenges of exascale computing, ultimately combing their efforts in a coordinated International Exascale Software Project.

e-Science and its implications

After a definition of e–science and the Grid, the paper begins with an overview of the technological context of Grid developments. NASAs Information Power Grid is described as an early example of a ‘prototype production Grid’. The discussion of e–science and the Grid is then set in the context of the UK e–Science Programme and is illustrated with reference to some UK e–science projects in science, engineering and medicine. The Open Standards approach to Grid middleware adopted by the community in the Global Grid Forum is described and compared with community–based standardization processes used for the Internet, MPI, Linux and the Web. Some implications of the imminent data deluge that will arise from the new generation of e–science experiments in terms of archiving and curation are then considered. The paper concludes with remarks about social and technological issues posed by Grid–enabled ‘collaboratories’ in both scientific and commercial contexts.

The International Exascale Software Project: a Call To Cooperative Action By the Global High-Performance Community

Over the last 20 years, the open-source community has provided more and more software on which the world’s high-performance computing systems depend for performance and productivity. The community has invested millions of dollars and years of effort to build key components. Although the investments in these separate software elements have been tremendously valuable, a great deal of productivity has also been lost because of the lack of planning, coordination, and key integration of technologies necessary to make them work together smoothly and efficiently, both within individual petascale systems and between different systems. A repository gatekeeper and an email discussion list can coordinate open-source development within a single project, but there is no global mechanism working across the community to identify critical holes in the overall software environment, spot opportunities for beneficial integration, or specify requirements for more careful coordination. It seems clear that this completely uncoordinated development model will not provide the software needed to support the unprecedented parallelism required for peta/exascale computation on millions of cores, or the flexibility required to exploit new hardware models and features, such as transactional memory, speculative execution, and GPUs. We believe the community must work together to prepare for the challenges of exascale computing, ultimately combing their efforts in a coordinated International Exascale Software Project.

MultiMATLAB Integrating MATLAB with High Performance Parallel Computing

MultiMATLAB is an extension of the popular MATLAB environment to distributed memory multiprocessors. We present a MultiMATLAB architecture that provides performance on multiprocessors while maintaining the functionality and usability of MATLAB. This system will enable users to access high performance parallel routines from within MATLAB, to extend MATLAB with new parallel routines, and to use these routines to develop parallel applications with the MATLAB language. We discuss a general MultiMATLAB architecture and present two implementations built upon MPI. Preliminary results indicate that the MultiMATLAB system can offer the full performance of the underlying multiprocessor to the MATLAB environment.

Energy-aware software: Challenges, opportunities and strategies

Abstract Energy consumption of computing systems has become a major concern. Constrained by cost, environmental concerns and policy, minimising the energy foot-print of computing systems is one of the primary goals of many initiatives. As we move towards exascale computing, energy constraints become very real and are a major driver in design decisions. The issue is also apparent at the scale of desk top machines, where many core and accelerator chips are common and offer a spectrum of opportunities for balancing energy and performance. Conventionally, approaches for reducing energy consumption have been either at the operational level (such as powering down all or part of systems) or at the hardware design level (such as utilising specialised low-energy components). In this paper, we are interested in a different approach; energy-aware software. By measuring the energy consumption of a computer application and understanding where the energy usage lies, may allow a change of the software to provide opportunities for energy savings. In order to understand the complexities of this approach, we specifically look at multithreaded algorithms and applications. By an evaluation of a benchmark suite on multiple architectures and multiple environments, we show how basic parameters, such as threading options, compilers and frequencies, can impact energy consumption. As such, we provide an overview of the challenges that face software developers in this regard. We then offer a view of the directions that need to be taken and possible strategies needed for building energy-aware software.

Rule-based visual mappings - with a case study on poetry visualization

In this paper, we present a user‐centered design study on poetry visualization. We develop a rule‐based solution to address the conflicting needs for maintaining the flexibility of visualizing a large set of poetic variables and for reducing the tedium and cognitive load in interacting with the visual mapping control panel. We adopt Munzners nested design model to maintain high‐level interactions with the end users in a closed loop. In addition, we examine three design options for alleviating the difficulty in visualizing poems latitudinally. We present several example uses of poetry visualization in scholarly research on poetry.

Spectra and pseudospectra for pipe Poiseuille flow

Abstract Numerically computed spectra and pseudospectra are presented for the linear operator that governs the temporal evolution of infinitesimal perturbations of laminar flow in an infinite circular pipe at Reynolds numbers 1000, 3000 and 10 000. The spectra lie strictly inside the stable complex half-plane, but the pseudospectra protrude significantly into the unstable half-plane, reflecting the large linear transient growth that certain perturbations may excite.

ShibGrid: Shibboleth Access for the UK National Grid Service

This paper presents work undertaken to integrate the future UK national Shibboleth infrastructure with the UKs National Grid Service (NGS). Our work, ShibGrid, provides both transparent authentication for portal based Grid access and a credential transformation service for users of other Grid access methods. The ShibGrid support for portal-based transparent Grid authentication is provided as a set of standards-based drop-in modules which can be used with any project portal as well as the NGS project in which they are initially deployed. The ShibGrid architecture requires no changes to the UK national Shibboleth authentication infrastructure or the NGS security infrastructure and provides access for users both with and without UK e-Science certificates. In addition to presenting both the architecture of Shib- Grid and its implementation, we additionally place the ShibGrid project within the context of other efforts to integrate Shibboleth with Grids.

Design and initial performance of a high-level unstructured mesh framework on heterogeneous parallel systems

Discuss the main design issues in parallelizing unstructured mesh applications.Present OP2 for developing applications for heterogeneous parallel systems.Analyze the performance gained with OP2 for two industrial-representative benchmarks.Compare runtime, scaling and runtime break-downs of the applications.Present energy consumption of OP2 applications on CPU and GPU clusters. OP2 is a high-level domain specific library framework for the solution of unstructured mesh-based applications. It utilizes source-to-source translation and compilation so that a single application code written using the OP2 API can be transformed into multiple parallel implementations for execution on a range of back-end hardware platforms. In this paper we present the design and performance of OP2s recent developments facilitating code generation and execution on distributed memory heterogeneous systems. OP2 targets the solution of numerical problems based on static unstructured meshes. We discuss the main design issues in parallelizing this class of applications. These include handling data dependencies in accessing indirectly referenced data and design considerations in generating code for execution on a cluster of multi-threaded CPUs and GPUs. Two representative CFD applications, written using the OP2 framework, are utilized to provide a contrasting benchmarking and performance analysis study on a number of heterogeneous systems including a large scale Cray XE6 system and a large GPU cluster. A range of performance metrics are benchmarked including runtime, scalability, achieved compute and bandwidth performance, runtime bottlenecks and systems energy consumption. We demonstrate that an application written once at a high-level using OP2 is easily portable across a wide range of contrasting platforms and is capable of achieving near-optimal performance without the intervention of the domain application programmer.

Lowering the Barriers to Cancer Imaging

There are various issues that limit the development and deployment of new software solutions in cancer image analysis research. In this paper we discuss some of these and propose a framework design based on cloud computing concepts, Microsoft technologies, existing middleware and imaging toolkits. Furthermore, we address some of these issues by introducing collaborative visual tools for visual input data and multi-user interactions.