apeNEXT: A multi-TFlops Computer for Simulations in Lattice Gauge Theory

We present the APE (Array Processor Experiment) project for the development of dedicated parallel computers for numerical simulations in lattice gauge theories. While APEmille is a production machine in today's physics simulations at various sites in Europe, a new machine, apeNEXT, is currently being developed to provide multi-Tflops computing performance. Like previous APE machines, the new supercomputer is largely custom designed and specifically optimized for simulations of Lattice QCD.Comment: Poster at the XXIII Physics in Collisions Conference (PIC03), Zeuthen, Germany, June 2003, 3 pages, Latex. PSN FRAP15. Replaced for adding forgotten autho

Задача о роботах на Марсе (мультиагентный подход к задаче Дейкстры)

We continue our study of multiagent algorithms for a problem that we call the Mars Robot Puzzle. This problem could be considered as a special case of a graph-theoretic problem (Discrete Mathematics), as a combinatorial geometry problem (Computer Science), or as a very special case of a path-planning problem (Artificial Intelligence). Our algorithms grew up from a local search (heuristic) solution of the problem suggested by E.W. Dijkstra. In the paper we present a series of new multiagent algorithms solving the problem, prove (manually) their correctness, model check some of these algorithms, and discuss further research topics. All our algorithms are multiagent in contrast to "centralized" graph and combinatorial algoritms; correctness of our algorithms is formally proven, while the testing is used for validation of path-planning algorithms.Изучаются мультиагентные алгоритмы для так называемой задачи о роботах на Марсе. Эту задачу можно рассматривать как задачу из теории графов (дискретная математика), как комбинаторную геометрическую задачу (теоретическое программирование) или как частный случай задачи планирования перемещений (искусственный интеллект). Наши алгоритмы основаны на эвристическом поиске, предложенном Э. Дейкстрой. В статье представлен ряд новых мультиагентных алгоритмов, решающих задачи о роботах на Марсе, доказана их корректность, приведены результаты проверки на модели некоторых из этих алгоритмов, предложены направления дальнейших исследований. Новизна представленной работы состоит в том, что в отличие от теоретико-графового и комбинаторно-геометрического подходов, ориентированных на централизованное решение задачи, мы развиваем мультиагентный подход, но, в свою очередь, наша работа отличается от работ по планированию перемещений математической строгостью доказательств корректности предложенных алгоритмов. Я, робот. А. Азимо

Statistical features of edge turbulence in RFX-mod from Gas Puffing Imaging

Plasma density fluctuations in the edge plasma of the RFX-mod device are measured through the Gas Puffing Imaging Diagnostics. Statistical features of the signal are quantified in terms of the Probability Distribution Function (PDF), and computed for several kinds of discharges. The PDFs from discharges without particular control methods are found to be adequately described by a Gamma function, consistently with the recent results by Graves et al [J.P. Graves, et al, Plasma Phys. Control. Fusion 47, L1 (2005)]. On the other hand, pulses with external methods for plasma control feature modified PDFs. A first empirical analysis suggests that they may be interpolated through a linear combination of simple functions. An inspection of the literature shows that this kind of PDFs is common to other devices as well, and has been suggested to be due to the simultaneous presence of different mechanisms driving respectively coherent bursts and gaussian background turbulence. An attempt is made to relate differences in the PDFs to plasma conditions such as the local shift of the plasma column. A simple phenomenological model to interpret the nature of the PDF and assign a meaning to its parameters is also developed.Comment: 27 pages. Published in PPC

Верификация алгоритмов мультиагентного анализа данных с помощью системы проверки моделей SPIN

The paper presents an approach to formal verification of multi-agent data analysis algorithms for ontology population. The system agents correspond to information items of the input data and the rule of ontology population and data processing. They determine values of information objects obtained at the preliminary phase of the analysis. The agents working in parallel check the syntactic and semantic consistency of tuples of information items. Since the agents operate in parallel, it is necessary to verify some important properties of the system related to it, such as the property that the controller agent correctly determines the system termination. In our approach, the model checking tool SPIN is used. The protocols of agents are written in Promela language (the input language of the tool) and the properties of the multi-agent data analysis system are expressed in the liner time logic LTL. We carried out several experiments to check this model in various modes of the tool and various numbers of agents.В статье представлен подход к формальной верификации алгоритмов мультиагентного анализа данных для пополнения онтологий. Агенты системы на основе входных данных устанавливают значения элементов объектов, полученных на предварительной стадии анализа. Агенты параллельно осуществляют проверку семантической и синтаксической согласованности, используя правила пополнения онтологий и обработки данных. Поскольку агенты действуют параллельно, необходимо верифицировать некоторые важные свойства системы, связанные с этим, например, свойство корректности определения завершения работы системы. В нашем подходе используется инструмент проверки моделей SPIN. Протоколы агентов записаны на языке Promela, а свойства мультиагентной системы анализа данных выражены в логике LTL. Мы провели ряд экспериментов по проверке данной модели

The apeNEXT project

Numerical simulations in theoretical high-energy physics (Lattice QCD) require huge computing resources. Several generations of massively parallel computers optimised for these applications have been developed within the APE (array processor experiment) project. Large prototype systems of the latest generation, apeNEXT, are currently being assembled and tested. This contribution explains how the apeNEXT architecture is optimised for Lattice QCD, provides an overview of the hardware and software of apeNEXT, and describes its new features, like the SPMD programming model and the C compiler

The apeNEXT project (Status report)

We present the current status of the apeNEXT project. Aim of this project is the development of the next generation of APE machines which will provide multi-teraflop computing power. Like previous machines, apeNEXT is based on a custom designed processor, which is specifically optimized for simulating QCD. We discuss the machine design, report on benchmarks, and give an overview on the status of the software development.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 8 pages, LaTeX, 12 eps figures. PSN THIT00

Taxing the Informal Economy: The Current State of Knowledge and Agendas for Future Research

This paper reviews the literature on taxation of the informal economy, taking stock of key debates and drawing attention to recent innovations. Conventionally, the debate on whether to tax has frequently focused on the limited revenue potential, high cost of collection, and potentially adverse impact on small firms. Recent arguments have increasingly emphasised the more indirect benefits of informal taxation in relation to economic growth, broader tax compliance, and governance. More research is needed, we argue, into the relevant costs and benefits for all, including quasi-voluntary compliance, political and administrative incentives for reform, and citizen-state bargaining over taxation

Status of the apeNEXT project

We present the current status of the apeNEXT project. Aim of this project is the development of the next generation of APE machines which will provide multi-teraflop computing power. Like previous machines, apeNEXT is based on a custom designed processor, which is specifically optimized for simulating QCD. We discuss the machine design, report on benchmarks, and give an overview on the status of the software development