An on‐line performance visualization technology

A new software technology for on‐line performance analysis and the visualization of complex parallel and distributed systems is presented. Often heterogeneous, these systems need capabilities for the flexible integration and configuration of performance analysis and visualization. Our technology is based on an object‐oriented framework for the rapid prototyping and development of distributable visual objects. The visual objects consist of two levels, a platform/device‐specific low level and an analysis‐ and visualization‐specific high level. We have developed a very high‐level markup language called VOML and a compiler for the component‐based development of high‐level visual objects. The VOML is based on a software architecture for on‐line event processing and performance visualization called EPIRA. The technology lends itself to constructing high‐level visual objects from globally distributed component definitions. Details of the technology and tools used, as well as how an example visual object can be rapidly prototyped from several reusable components, are presented. Copyright © 2003 John Wiley & Sons, Ltd.     

Low‐level PGAS computing on many‐core processors with TSHMEM

Diminishing returns from increased clock frequencies and instruction‐level parallelism have forced computer architects to adopt architectures that exploit wider parallelism through multiple processor cores. While emerging many‐core architectures have progressed at a remarkable rate, concerns arise regarding the performance and productivity of numerous parallel‐programming tools for application development. Development of parallel applications on many‐core processors often requires developers to familiarize themselves with unique characteristics of a target platform while attempting to maximize performance and maintain correctness of their applications. The family of partitioned global address space (PGAS) programming models comprises the current state of the art in balancing performance and programmability. One such PGAS approach is SHMEM, a lightweight, shared‐memory programming library that has demonstrated high performance and productivity potential for parallel‐computing systems with distributed‐memory architectures. In the paper, we present research, design, and analysis of a new SHMEM infrastructure specifically crafted for low‐level PGAS on modern and emerging many‐core processors featuring dozens of cores and more. Our approach (with a new library known as TSHMEM) is investigated and evaluated atop two generations of Tilera architectures, which are among the most sophisticated and scalable many‐core processors to date, and is intended to enable similar libraries atop other architectures now emerging. In developing TSHMEM, we explore design decisions and their impact on parallel performance for the Tilera TILE‐Gx and TILEPro many‐core architectures, and then evaluate the designs and algorithms within TSHMEM through microbenchmarking and applications studies with other communication libraries. Our results with barrier primitives provided by the Tilera libraries show dissimilar performance between the TILE‐Gx and TILEPro; therefore, TSHMEM's barrier design takes an alternative approach and leverages the on‐chip mesh network to provide consistent low‐latency performance. In addition, our experiments with TSHMEM show that naive collective algorithms consistently outperformed linear distributed collective algorithms when executed in an SMP‐centric environment. In leveraging these insights for the design of TSHMEM, our approach outperforms the OpenSHMEM reference implementation, achieves similar to positive performance over OpenMP and OSHMPI atop MPICH, and supports similar libraries in delivering high‐performance parallel computing to emerging many‐core systems. Copyright © 2015 John Wiley & Sons, Ltd.     

SIMCAN: A flexible, scalable and expandable simulation platform for modelling and simulating distributed architectures and applications

In this paper we propose a new simulation platform called SIMCAN, for analyzing parallel and distributed systems. This platform is aimed to test parallel and distributed architectures and applications. The main characteristics of SIMCAN are flexibility, accuracy, performance, and scalability. Thence, the proposed platform has a modular design that eases the integration of different basic systems on a single architecture. Its design follows a hierarchical schema that includes simple modules, basic systems (computing, memory managing, I/O, and networking), physical components (nodes, switches, …), and aggregations of components. New modules may also be incorporated as well to include new strategies and components. Also, a graphical configuration tool has been developed to help untrained users with the task of modelling new architectures. Finally, a validation process and some evaluation tests have been performed to evaluate the SIMCAN platform.     

A comprehensive analytical model of interconnection networks in large‐scale cluster systems

The trends in parallel processing system design and deployment have been toward networked distributed systems such as cluster computing systems. Since the overall performance of such distributed systems often depends on the efficiency of their communication networks, performance analysis of the interconnection networks for such distributed systems is paramount. In this paper, we develop an analytical model, under non‐uniform traffic and in the presence of communication locality, for the m‐port n‐tree family interconnection networks commonly employed in large‐scale cluster computing systems. We use the proposed model to study two widely used interconnection networks flow control mechanism namely the wormhole and store&forward. The proposed analytical model is validated through comprehensive simulation. The results of the simulation demonstrated that the proposed model exhibits a good degree of accuracy for various system organizations and under different working conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Designing an adaptive computer‐aided ambulance dispatch system with Zanshin: an experience report

We have been witnessing growing interest in systems that can adapt their behavior to deal with deviations between their performance and their requirements at run‐time. Such adaptive systems usually need to support some form of a feedback loop that monitors the system's output for problems and carries out adaptation actions when necessary. Being an important feature, adaptivity needs to be considered in early stages of development. Therefore, adopting a requirements engineering perspective, we have proposed an approach and a framework (both called Zanshin) for the engineering of adaptive systems based on a feedback loop architecture. As part of our framework's evaluation, we have applied the Zanshin approach to the design of an adaptive computer‐aided ambulance dispatch system, whose requirements were based on a well‐known case study from the literature. In this paper, we report on the application of Zanshin for the design of an adaptive computer‐aided ambulance dispatch system, presenting elements of the design, as well as the results from simulations of run‐time scenarios. Copyright © 2013 John Wiley & Sons, Ltd.     

Distributed loop‐scheduling schemes for heterogeneous computer systems

Distributed computing systems are a viable and less expensive alternative to parallel computers. However, a serious difficulty in concurrent programming of a distributed system is how to deal with scheduling and load balancing of such a system which may consist of heterogeneous computers. Some distributed scheduling schemes suitable for parallel loops with independent iterations on heterogeneous computer clusters have been designed in the past. In this work we study self‐scheduling schemes for parallel loops with independent iterations which have been applied to multiprocessor systems in the past. We extend one important scheme of this type to a distributed version suitable for heterogeneous distributed systems. We implement our new scheme on a network of computers and make performance comparisons with other existing schemes. Copyright © 2005 John Wiley & Sons, Ltd.     

Tool integration for flexible simulation of distributed algorithms

Over the last two decades, considerable research has been done in distributed operating systems, which can be attributed to faster processors and better communication technologies. A distributed operating system requires distributed algorithms to provide basic operating system functionality like mutual exclusion, deadlock detection, etc. A number of such algorithms have been proposed in the literature. Traditionally, these distributed algorithms have been presented in a theoretical way, with limited attempts to simulate actual working models. This paper discusses our experience in simulating distributed algorithms with the aid of some existing tools, including OPNET and Xplot. We discuss our efforts to define a basic model‐based framework for rapid simulation and visualization, and illustrate how we used this framework to evaluate some classic algorithms. We have also shown how the performance of different algorithms can be compared based on some collected statistics. To keep the focus of this paper on the approach itself, and our experience with tool integration, we only discuss some relatively simple models. Yet, the approach can be applied to more complex algorithm specifications. Copyright © 2001 John Wiley & Sons, Ltd.     

Interactive Simulation of Rigid Body Dynamics in Computer Graphics

Interactive rigid body simulation is an important part of many modern computer tools, which no authoring tool nor game engine can do without. Such high‐performance computer tools open up new possibilities for changing how designers, engineers, modelers and animators work with their design problems. This paper is a self contained state‐of‐the‐art report on the physics, the models, the numerical methods and the algorithms used in interactive rigid body simulation all of which have evolved and matured over the past 20 years. Furthermore, the paper communicates the mathematical and theoretical details in a pedagogical manner. This paper is not only a stake in the sand on what has been done, it also seeks to give the reader deeper insights to help guide their future research.     

Revisiting conservative time synchronization protocols in parallel and distributed simulation

Computer simulations have become an indispensable tool for the empirical study of large‐scale systems. The timely simulation of these systems, however, is not without its challenges. Simulators have to be able to harness the full computational power of modern multicore architectures through parallel execution and overcome the memory limitations of a single computer. In this paper, we evaluate the performance of a parallel and distributed simulator using several conventional time synchronization protocols executed on modern multicore hardware. In addition, we comprehensively analyze a hybrid approach, combining two traditional protocols, increasing robustness, and enabling improved performance in a wider range of simulation scenarios. Finally, an adaptive algorithm to automatically configure this hybrid protocol is introduced and evaluated, eliminating manual user intervention and further improving robustness with respect to varying simulation conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

Modular Design of Real-Time Systems Using Hierarchical Communicating Real-time State Machines

This paper proposes a methodology for the development of distributed real-time systems. The methodology consists of the Hierarchical Communicating Real-Time State Machines (H-CRSM) modelling language, and the Violin toolset. H-CRSM combines Statecharts constructs with CSP-like timed communications. Violin provides a visual environment supporting in a seamless way all the life-cycle development phases of an H-CRSM system. Temporal validation rests on assertion checking during system simulation. Code generation is based on Java and a customizable runtime. The practical use of H-CRSM/Violin is shown by an example. A preliminary version of this paper appears in Proc. of Joint Modular Languages Conference (JMLC'2003), Klagenfurt, Austria, August 2003, LNCS 2789, Springer, pp. 110–121. Angelo Furfaro, Phd, is a computer science assistant professor at Unical, DEIS, teaching object-oriented programming. His research interests include: multiagent systems, Petri nets, parallel simulation, verification of time-dependent systems, distributed measurement systems. He is a member of ACM. Libero Nigro is a full professor of computer science at Unical, DEIS, where he teaches object-oriented programming, software engineering and real-time systems courses. He is the responsible of Software Engineering Laboratory (www.lis.deis.unical.it). His current research interests include: software engineering of time-dependent and distributed systems, real-time systems, Petri nets, modeling and parallel simulation of complex systems, distributed measurement systems. Prof. Nigro is a member of ACM and IEEE. Francesco Pupo, Phd, is a computer science assistant professor at Unical, DEIS, teaching introductory programming and computer architecture courses. His research interests include: Petri nets, discrete-event simulation, real-time systems, distributed measurement systems.     

Distributed robust control of uncertain linear multi‐agent systems

In this paper, the distributed H _∞ robust control problem synthesized with transient performance is investigated for a group of autonomous agents governed by uncertain general linear node dynamics. Based on the relative information between neighboring agents and some information of other agents, distributed state‐feedback and observer‐type output‐feedback control protocols are designed and analyzed, respectively. By using tools from robust control theory, conditions for the existence of controllers for solving such a problem are established. It is shown that the problem of distributed H _∞ robust control synthesized with transient performance can be converted to the H _∞ control problem synthesized with transient performance for decoupled linear systems of the same low dimensions. Finally, simulation examples are provided to illustrate the effectiveness of the design. Copyright © 2014 John Wiley & Sons, Ltd.     

Design evaluation and modification of mechanical systems in virtual environments

Design is one of the most important stages in the manufacturing cycle and influences all the subsequent stages of product development. In the context of today’s iterative design methodology, the modification of any design is a process involving many evaluations and improvements to the solutions chosen in earlier stages. For this purpose, in the most recent decade, 3D computer simulations have become common tools used within industry. Whilst virtual reality (VR) technology is seen as the interaction technology of the future, much of the current research in this area is carried out to explore the potential benefits and added value brought by the integration of this into standard software technologies currently used at various stages in manufacturing life cycle. A lot of attention has been given to exploring the usability and benefits of interactive VR for assembly planning, knowledge elicitation and design and simulation. However, little research has focussed on the analytical aspects of the design process, for example in the use of VR as an interface for simulation software in finite element methods and multi-body systems. This paper introduces research focussing on applications of virtual environments (VEs) for interactive design evaluation and modification adapted and used with standard simulation software. The use of such interactive visualisation offers the engineer more realistic real-time representations of the design and advanced facilities to interact with the model during the design process. While design evaluation is based mainly on visualisation; design modification requires interactive changes of the model during the simulation, and the interfaces described here highlights such applications. In this work, two software prototypes have been developed using VR technology. First, a software tool called design evaluation in virtual environments is presented together with an application in civil engineering to illustrate the mode of operation and added value of the use of an interactive visualisation environment. Linking the simulation software with the VE provides real time bi-directional communication of graphical information which can be successfully achieved even within the limits of current computer technology. The tool includes a suite of software modules and a user interface to facilitate the link between the simulation results and the VE. The second tool facilitates the design modification in virtual environments system by providing real time dynamic simulation. Two dynamic approaches are investigated in order to study the real time simulation issues in the context of design modification and system performance: the classic approach based on rigid interconnected bodies, and a new and novel approach developed by the authors based on particles dynamics. Both implementations have been tested and compared on a mechanism application under the same computing conditions. The research applications presented demonstrate the practicality, flexibility and versatility of the visualisation in virtual environment in design evaluation and modification. However, the computer efficiency whilst carrying out real time dynamic simulation is limiting the range of applications to models of moderate size; however, this is an improvement on previous similar applications.     

EPPOD: A Problem Solving Environment for Parallel Electronic Prototyping of Physical Object Design

One of the grand challenges for computer applications is the creation of a system that will provide accurate computer simulations of physical objects coupled with powerful design optimization tools to allow optimum prototyping and the final design of a broad range of physical objects. We refer to such a software environment aselectronic prototyping for physical object design (EPPOD). The research challenges in building such systems are in softwareintegration, in utilizingmassive parallelismto satisfy their large computational requirements, in incorporatingknowledgeinto the entire electronic prototyping process, in creatingintelligentuser interfaces for such systems, and in advancing thealgorithmic infrastructureneeded to support the desired functionality. In this paper we address issues related to the parallel processing of the computationally intensive components of the EPPOD problem solving environment on message passing parallel machines and present its software architecture. The parallel methodology adopted to map the underlying computations to parallel machines is based on the optimal decomposition of continuous and discrete geometric data associated with the physical object. One of the main goals of this methodology is thereuseof existing software parts while implementing various components of the EPPOD system on parallel computational environments. Finally, some performance data of the parallel algorithmic infrastructured developed are listed and discussed.     

一种均衡可扩展计算机体系结构分布式模拟方法

分布式并行模拟是提高体系结构模拟速度的有效技术手段之一.首先,建立了分布式并行模拟的通用性能分析模型,并对典型系统的并行加速比、并行效率等性质进行了理论分析,得出了一些有用的结论.在此基础上,提出了均衡可扩展分布式并行模拟方法SEDSim（scalable and evenly distributed simulation）.SEDSim 针对模拟节点负载不均衡问题,提出了开销模型指导的指令区间均衡分割和分配策略CoMEPA（cost model guided evenly partitionand allocation）;针对分布式并行模拟与非连续、任意数量抽样模拟区间的高效集成,提出了基于最小等价距离（minimum equivalent cost,简称MinEC）的指令区间分配策略MinEC.基于sim-outorder 实现了SEDSim,采用SPECCPU2000 中的部分程序对其速度和精度进行了测试,理论分析和测试结果均表明了SEDSim 的优势：相对于常用的方法或策略,CoMEPA 和MinEC 分别能够获得多达约1.6 倍和1.4 倍的性能提升.     

基于分布对象的并行程序设计方法研究

研究分布式对象的并行实现及优化,提出一种基于分布式对象的并行程序设计方法,构建一个基于分布式对象的并行程序设计模型,并以此方法完成虚拟计算机网络实验系统的设计和实现实验结果表明,该虚拟计算机网络实验系统并行性较好、响应速度适中,证明基于分布式对象的并行程序设计方法在改善微机系统并行性上具有一定的作用     

The Failure Trace Archive: Enabling the comparison of failure measurements and models of distributed systems

With the increasing presence, scale, and complexity of distributed systems, resource failures are becoming an important and practical topic of computer science research. While numerous failure models and failure-aware algorithms exist, their comparison has been hampered by the lack of public failure data sets and data processing tools. To facilitate the design, validation, and comparison of fault-tolerant models and algorithms, we have created the Failure Trace Archive (FTA)—an online, public repository of failure traces collected from diverse parallel and distributed systems. In this work, we first describe the design of the archive, in particular of the standard FTA data format, and the design of a toolbox that facilitates automated analysis of trace data sets. We also discuss the use of the FTA for various current and future purposes. Second, after applying the toolbox to nine failure traces collected from distributed systems used in various application domains (e.g., HPC, Internet operation, and various online applications), we present a comparative analysis of failures in various distributed systems. Our analysis presents various statistical insights and typical statistical modeling results for the availability of individual resources in various distributed systems. The analysis results underline the need for public availability of trace data from different distributed systems. Last, we show how different interpretations of the meaning of failure data can result in different conclusions for failure modeling and job scheduling in distributed systems. Our results for different interpretations show evidence that there may be a need for further revisiting existing failure-aware algorithms, when applied for general rather than for domain-specific distributed systems.     

Scalable shared memory LTL model checking

Recent development in computer hardware has brought more widespread emergence of shared memory, multi-core systems. These architectures offer opportunities to speed up various tasks—model checking and reachability analysis among others. In this paper, we present a design for a parallel shared memory LTL model checker that is based on a distributed memory algorithm. To improve the scalability of our tool, we have devised a number of implementation techniques which we present in this paper. We also report on a number of experiments we conducted to analyse the behaviour of our tool under different conditions using various models. We demonstrate that our tool exhibits significant speedup in comparison with sequential tools, which improves the workflow of verification in general.     

Simulation and computer-aided kinematic design of three-degree-of-freedom spherical parallel manipulators

Parallel robotic manipulators are complex mechanical systems that lead to involved kinematic and dynamic equations. Hence, the design of such systems is in general not intuitive, and advanced simulation and design tools specialized for this type of architecture are highly desirable. This article discusses the kinematic simulation and computer-aided design of three-degree-of-freedom spherical parallel manipulators with either prismatic or revolute actuators. The kinematic analysis of spherical parallel manipulators is first reviewed. Solutions for the direct and inverse kinematic problems are given, and the expressions for the singularity loci are then introduced. The determination of the workspace of this type of manipulator is also addressed. Finally, a computer package developed specifically for the CAD of spherical parallel manipulators is presented. This package allows the interactive analysis of manipulators of arbitrary architecture including the representation of the workspace, the representation of singularities, and the graphic animation of trajectories specified either by the direct or the inverse kinematic module. It can be used for the design of any spherical parallel three-degree-of-freedom actuated mechanism, which can find many applications in high-performance robotic systems. © 3995 John Wiley & Sons, Inc.     

ArchSim: A System-Level Parallel Simulation Platform for the Architecture Design of High Performance Computer

High performance computer (HPC) is a complex huge system, of which the architecture design meets increasing difficulties and risks. Traditional methods, such as theoretical analysis, component-level simulation and sequential simulation, are not applicable to system-level simulations of HPC systems. Even the parallel simulation using large-scale parallel machines also have many difficulties in scalability, reliability, generality, as well as efficiency. According to the current needs of HPC architecture design, this paper proposes a system-level parallel simulation platform: ArchSim. We first introduce the architecture of ArchSim simulation platform which is composed of a global server (GS), local server agents (LSA) and entities. Secondly, we emphasize some key techniques of ArchSim, including the synchronization protocol, the communication mechanism and the distributed checkpointing/restart mechanism. We then make a synthesized test of some main performance indices of ArchSim with the phold benchmark and analyze the extra overhead generated by ArchSim. Finally, based on ArchSim, we construct a parallel event-driven interconnection network simulator and a system-level simulator for a small scale HPC system with 256 processors. The results of the performance test and HPC system simulations demonstrate that ArchSim can achieve high speedup ratio and high scalability on parallel host machine and support system-level simulations for the architecture design of HPC systems.     

高可用CORBA

CORBA是OMG组织提出的一个基于OMA体系结构的分布式系统,是当前面向对象分布式系统中的典型代表。基于CORBA规范的分布式系统如IONA的Orbix、Inprise的Visibroker的产品等已经不断推向市场,CORBA在分布式环境中为解决异质环境的应用提供了良好的基础平台,用户在开发过程中不用考虑低层复杂的分布式环境,而把主要的精力放在高层。随着对CORBA的研究与开发,人们对其可靠性提出了更高的要求,于是如何建立基于CORBA环境