Computational physics with PetaFlops computers

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Abstract

Driven by technology, Scientific Computing is rapidly entering the PetaFlops era. The Jülich Supercomputing Centre (JSC), one of three German national supercomputing centres, is focusing on the IBM Blue Gene architecture to provide computer resources of this class to its users, the majority of whom are computational physicists. Details of the system will be discussed and applications will be described which significantly benefit from this new architecture.

Introduction

In many areas of physics, numerical simulation has become an essential tool for advancing theoretical research. Driven by the rapid development in computer technology, this insight has dramatically raised the expectations of computational scientists with respect to application performance, memory, data storage, and data transfer capabilities [1], [2]. Currently, only high-performance supercomputers with a large number of processors are capable to fulfil these needs.

The Jülich Supercomputing Centre has implemented a dual supercomputer strategy to provide computational scientists with adequate computing resources. First, a general-purpose supercomputer, currently realised as a moderately parallel cluster with a peak performance of 8.4 TeraFlop/s serves about 150 German and European user groups from universities and research institutions. This system allows the development of parallel codes as well as the execution of small to mid-size projects. Second, for applications which scale-up to ten thousands of processors (capability computing) and which tackle Grand Challenge problems, an IBM Blue Gene system with a peak performance of 223 TeraFlop/s is available, serving as a leadership-class system and geared to petascale problems. On this system, a much smaller number of projects are granted to give selected researchers the opportunity to get new insights into complex problems which were out of reach before. Both supercomputer systems are integrated in a common user environment and have access to a common general parallel file system, a functionality which is provided by a dedicated file server.

Section snippets

Integration of JSC in existing HPC networks and alliances

Since 1986 the primary mission of the Jülich Supercomputing Centre has been the provision of supercomputer resources of the highest performance class to the scientific and engineering research communities at national and European universities and research institutions. This includes the provision of a state-of-the-art technical infrastructure as well as an optimal user support.

The appropriate allocation of the corresponding resources is ensured by an international peer-review process.

IBM Blue Gene systems at JSC

When the IBM Blue Gene technology became available in 2004/2005, the Jülich Supercomputing Centre quickly recognised the potential of this architecture as a Leadership-class system for capability computing applications. In early summer 2005, Jülich started testing a single Blue Gene/L rack with 2048 processors [6]. It soon became obvious that many more applications than initially expected were ported to efficiently run on the Blue Gene architecture. Therefore, in January 2006 the system was

User support

With the increasing prevalence of architectures based on massively parallel and multi-core processor topologies, many simulation scientists are compelled to take scalability into account when developing new models or when porting long-established codes to machines like the Blue Gene. This poses significant problems for the small research groups making up the majority of users of the JSC computing facilities, which typically do not have the resources or expertise for application petascaling. To

Running applications on Blue Gene

Due to the fact that the Blue Gene architecture is well-balanced in terms of processor speed, memory latency, and network performance, parallel applications scale reasonably on these systems up to large numbers of processors. However, it is surprising how many applications can be ported to and run efficiently on this new architecture which in a forerunner version was mainly designed to perform lattice quantum chromo dynamics (LQCD) codes. Blue Gene applications at JSC cover a broad spectrum

Summary

In this contribution the rapid development in computer technology and its impacts were introduced. It was discussed that only centres that are fully imbedded in local, regional, national and international (European) networks and alliances are able to provide supercomputing resources of the highest performance class continuously. The Jülich Supercomputing Centre JSC in Germany is such a centre and it concentrates today on leadership-class supercomputers of the type IBM Blue Gene making PetaFlops

Acknowledgements

The author would like to thank the organisers of the Conference on Computational Physics (CCP 2008) for inviting him and for providing the possibility to present his experiences with large-scale Blue Gene systems to a broad scientific audience. The author would also like to thank Alessandro Curioni, Rüdiger Esser, Paul Gibbon, Stefan Krieg and Dominik Marx for stimulating discussions on this topic.

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