Section: Overall Objectives

Introduction

Over the last few decades, there have been innumerable science, engineering and societal breakthroughs enabled by the development of high performance computing (HPC) applications, algorithms and architectures. These powerful tools have provided researchers with the ability to computationally find efficient solutions for some of the most challenging scientific questions and problems in medicine and biology, climatology, nanotechnology, energy and environment. It is admitted today that numerical simulation is the third pillar for the development of scientific discovery at the same level as theory and experimentation. Numerous reports and papers also confirmed that very high performance simulation will open new opportunities not only for research but also for a large spectrum of industrial sectors (see for example the documents available on the web link http://science.energy.gov/ascr/news-and-resources/program-documents/ ).

An important force which has continued to drive HPC has been to focus on frontier milestones which consist in technical goals that symbolize the next stage of progress in the field. In the 1990s, the HPC community sought to achieve computing at a teraflop rate and currently we are able to compute on the first leading architectures at a petaflop rate. Generalist petaflop supercomputers are likely to be available in 2010-2012 and some communities are already in the early stages of thinking about what computing at the exaflop level would be like.

For application codes to sustain a petaflop and more in the next few years, hundreds of thousands of processor cores or more will be needed, regardless of processor technology. Currently, a few HPC simulation codes easily scale to this regime and major code development efforts are critical to achieve the potential of these new systems. Scaling to a petaflop and more will involve improving physical models, mathematical modelling, super scalable algorithms that will require paying particular attention to acquisition, management and vizualization of huge amounts of scientific data.

In this context, the purpose of the HiePACS project is to perform efficiently frontier simulations arising from challenging research and industrial multiscale applications. The solution of these challenging problems require a multidisciplinary approach involving applied mathematics, computational and computer sciences. In applied mathematics, it essentially involves advanced numerical schemes. In computational science, it involves massively parallel computing and the design of highly scalable algorithms and codes to be executed on emerging petaflop (and beyond) platforms. Through this approach, HiePACS intends to contribute to all steps that go from the design of new high-performance more scalable, robust and more accurate numerical schemes to the optimized implementations of the associated algorithms and codes on very high performance supercomputers. This research will be conduced on close collaboration in particular with European and US initiatives or projects such as PRACE (Partnership for Advanced Computing in Europe – http://www.prace-project.eu/ ), EESI (European Exascale Software Initiative – http://www.eesi-project.eu/pages/menu/homepage.php ) or IESP (International Exascale Software Project – http://icl.cs.utk.edu/iesp/Main_Page ).

In order to address these research challenges, some of the researchers of the former ScAlApplix Inria Project-Team and some researchers of the Parallel Algorithms Project from CERFACS have joined HiePACS in the framework of the joint Inria-CERFACS Laboratory on High Performance Computing. The director of the joint laboratory is J. Roman while I.S. Duff is the senior scientific advisor. HiePACS is the first research initiative of this joint Laboratory. Because of his strong involvement in RAL and his oustanding action in other main initiatives in UK and wordwide, I.S. Duff appears as an external collaborator of the HiePACS project while his contribution will be significant. There are two other external collaborators. Namely, P. Fortin who will be mainly involved in the activities related to the parallel fast multipole development and G. Latu who will contribute to research actions related to the emerging new computing facilities.

The methodological part of HiePACS covers several topics. First, we address generic studies concerning massively parallel computing, the design of high-end performance algorithms and software to be executed on future petaflop (and beyond) platforms. Next, several research prospectives in scalable parallel linear algebra techniques are adressed, in particular hybrid approaches for large sparse linear systems. Then we consider research plans for N-body interaction computations based on efficient parallel fast multipole methods and finally, we adress research tracks related to the algorithmic challenges for complex code couplings in multiscale simulations.

Currently, we have one major multiscale application that is in material physics. We contribute to all steps of the design of the parallel simulation tool. More precisely, our applied mathematics skill will contribute to the modelling and our advanced numerical schemes will help in the design and efficient software implementation for very large parallel multiscale simulations. Moreover, the robustness and efficiency of our algorithmic research in linear algebra are validated through industrial and academic collaborations with different partners involved in various application fields.

Our high performance software packages are integrated in several academic or industrial complex codes and are validated on very large scale simulations. For all our software developments, we use first the various (very) large parallel platforms available through CERFACS and GENCI in France (CCRT, CINES and IDRIS Computational Centers), and next the high-end parallel platforms that will be available via European and US initiatives or projects such that PRACE.