B. Guillerminet

Tore Supra continuous acquisition system

As part of the request to run 1000 s plasma discharges in the near future at Tore Supra, a study was launched in late 1998 to identify the limitations of the present acquisition system with respect to long pulse operation. Since our initial study and proposal, new requirements have arisen which lead us not just to long duration but to continuous operation. In the first part of this paper, we recall the specific problems with long duration discharges and the new requests. In the second part, the solutions for continuous operation are described and finally, we present the Tore Supra implementation and outline the current status and planning.

Approaches to Distributed Execution of Scientific Workflows in Kepler

The Kepler scientific workflow system enables creation, execution and sharing of workflows across a broad range of scientific and engineering disciplines while also facilitating remote and distributed execution of workflows. In this paper, we present and compare different approaches to distributed execution of workflows using the Kepler environment, including a distributed data-parallel framework using Hadoop and Stratosphere, and Cloud and Grid execution using Serpens, Nimrod/K and Globus actors. We also present real-life applications in computational chemistry, bioinformatics and computational physics to demonstrate the usage of different distributed computing capabilities of Kepler in executable workflows. We further analyze the differences of each approach and provide a guidance for their applications.

Tore supra data acquisition: A system for long duration discharges

The Tore supra data acquisition system has been completely re-engineered (Guillerminet et al., 1996, Proceedings of the 19th Symposium on Fusion Technology, Lisbonne, 1996) over the last few years as part of the long duration discharge programme, and has been in operation since autumn 1996. It is based on a commercial package which provides all the basic modules required to build a distributed on-line software system, integrating the parameter loading, control, data acquisition, and real-time data displays. In this paper we examine the whole system, analyse the requirements to achieve continuous operation and discuss the favoured solution for Tore supra.

The acquisition system for Tore Supra 1000 s discharges

Abstract Long duration discharges are planned for Tore Supra in the near future. A study has been made to detect and correct all the possible limitations of the data acquisition system. Results and analysis of a few 1000 s ‘dry-run’ test pulses are presented in this paper as well as the solutions foreseen for Tore Supra.

Design and first applications of the ITER integrated modelling & analysis suite

The ITER Integrated Modelling & Analysis Suite (IMAS) will support both plasma operation and research activities on the ITER tokamak experiment. The IMAS will be accessible to all ITER members as a key tool for the scientific exploitation of ITER. The backbone of the IMAS infrastructure is a standardized, machine-generic data model that represents simulated and experimental data with identical structures. The other outcomes of the IMAS design and prototyping phase are a set of tools to access data and design integrated modelling workflows, as well as first plasma simulators workflows and components implemented with various degrees of modularity.

New developments of the TORE SUPRA acquisition system

In order to support the heat-load of a continuous high power plasma, the upgrade of the first wall of the TORE SUPRA tokamak is now in progress and the first pulses are expected by July 2001. The TORE SUPRA acquisition system, originally conceived for long pulse data acquisition and processing, needs some improvements to meet new requirements such as fast and continuous data access, real time data processing where possible, more efficient post-pulse data processing.

Tools, Methods and Services Enhancing the Usage of the Kepler-based Scientific Workflow Framework

Abstract Scientific workflow systems are designed to compose and execute either a series of computational or data manipulation steps, or workflows in a scientific application. They are usually a part of a larger eScience environment. The usage of workflow systems, however very beneficial, is mostly not irrelevant for scientists. There are many requirements for additional functionalities around scientific workflows systems that need to be taken into account, like the ability of sharing workflows, provision of the user-friendly GUI tools for automation of some tasks or submission to distributed computing infrastructures, etc. In this paper we present tools developed in response to the requirements of three different scientific communities. These tools simplify and empower their work with the Kepler scientific workflow system. The usage of such tools and services is presented on Nanotechnology, Astronomy and Fusion scenarios examples.

A European Infrastructure for Fusion Simulations

The Integrated Tokamak Modelling Task Force (ITM-TF) is developing an infrastructure where the validation needs, as being formulated in terms of multi-device data access and detailed physics comparisons aiming for inclusion of synthetic diagnostics in the simulation chain, are key components. A device independent approach to data transport and a standardized approach to data management (data structures, naming, and access) is being developed in order to allow cross validation between different fusion devices using a single toolset. The effort is focused on ITER plasmas and ITER scenario development on current fusion device. The modeling tools are, however, aimed for general use and can be promoted in other areas of modelling as well. Extensive work has already gone into the development of standardized descriptions of the data (Consistent Physical Objects) providing initial steps towards a complete fusion modelling ontology. The longer term aim is a complete simulation platform which is expected to last and be extended in different ways for the coming 30 years. The technical underpinning is therefore of vital importance. In particular, the platform needs to be extensible and open-ended to be able to take full advantage of not only today’s most advanced technologies but also be able to marshal future developments. A full level comprehensive prediction of ITER physics rapidly becomes expensive in terms of computing resources and may cover a range of computing paradigms. The simulation framework therefore needs to be able to use both grid and HPC computing facilities. Hence, data access and code coupling technologies are required to be available for a heterogeneous, possibly distributed, environment. The developments in this area are pursued in a separate project - EUFORIA (EU Fusion for ITER Applications). The current status of ITM-TF and EUFORIA is presented and discussed.

Parallel universal access layer: A scalable I/O library for integrated tokamak modeling

Abstract The paper describes a parallel-I/O extension of the Universal Access Layer, a multi-language interface used for exchange of standardized data objects between Integrated Tokamak Modeling (ITM) codes. Although our evaluation focuses on Lustre, the general idea also applies to other parallel file systems. A snapshot of the current implementation is given, followed by an analysis of user and system requirements. The design derived from the serial version of the UAL is described, and emphasized features such as the ability to choose between serial and parallel I/O are explained. Performance tests comparing the implementation to other I/O methods are made to analyze the impact of the implementation. The outcome shows that the new implementation not only enables the I/O of datasets with several GB in size but also speeds up the write rate by a factor of 13 in the best case.

High level tools for fusion simulations workflows in distributed computing environment

This paper describes chosen aspects of the European Integrated Tokamak Modelling Task Force (ITM-TF) effort. It covers topics related to latest developments towards providing fusion scientists with a software framework for fusion modeling and simulation. The proposed framework provides researchers with an easy to use, workflow based environment for scientific computations. It allows the execution of various applications in numerous distributed computational resources directly from a user friendly, intuitive interface. We present the latest advances in the development of easy to use tools allowing the integration of the physics codes into the scientific workflows that schedule jobs to different infrastructures. The presented approach provides a simple way to access extensive computational resources and hides the complexity of the process at the same time. It allows for easy extension of existing simulation scenarios and fast prototyping. Some aspects of interactive communication between workflow environment and running jobs are discussed. Results of two practical use cases are presented in the context of the discussed workflow based solution: a parametric study and a plasma turbulence workflow.