The Professional Workstation Research Project

Powerful, inexpensive processors, low-cost storage, and high-resolution color displays make single-user, networked, multiprogrammed computer workstations suitable replacements for the time-shared mainframe environment of the scientific and engineering professional. Distributed processing via networks of workstations connected to larger server machines, which are in turn connected to national and international networks, allows a completely new form of computer-aided organization for institutions. The flexibility and speed of such machines mean that a new revolution in information processing and human activity support is inevitable. The professional workstation project has as its immediate goal a networked, distributed system of single-user workstations. Each will use the Unix operating system and provide powerful object-oriented graphics tools that will enhance the productivity of scientific and engineering professionals.     

Linux in practice: an overview of applications

The article discusses several interesting applications of Linux, in a wide variety of environments. These include an oceanographic lab running remote and inaccessible sensors, the development of a high-speed network on a shoestring budget, a publishing company that evolved from two people and a Unix box to 15 people on Linux workstations, the development of “soft real-time” control systems in Europe and South America, a military contractor building complex real-time embedded applications, and the use of a Beowulf cluster computer for supercomputing tasks such as weather simulation     

An evaluation of PCs for high energy physics under Windows NT and Linux

The high availability and commodity prices of Intel-based PCs have made them serious contenders to workstations. We address the question whether PCs are appropriate for running real physics codes. We evaluate the performance of Intel-based systems with two popular 32-bit operating systems, Linux and Windows NT. We report on a suite of benchmark tests, both generic and HEP-specific, where we compare the performance of these two systems to each other, and to other popular workstation class machines.     

Runtime Support for Parallelization of Data-Parallel Applications on Adaptive and Nonuniform Computational Environments

In this paper we discuss the runtime support required for the parallelization of unstructured data-parallel applications on nonuniform and adaptive environments. We describe several optimization techniques for fast remapping of data and for reducing the amount of communications between machines when the computational load on the machines changes during the execution of data-parallel applications. The approach presented is reasonably general and is applicable to a wide variety of regular as well as irregular applications. We present performance results for the solution of an unstructured mesh on a cluster of workstations.     

DJM: a global distributed virtual machine on the Internet

In this paper, we present the design and implementation of a novel model of distributed computing on the Internet and Intranet environment. Our model is called the Distributed Java Machine (DJM). It is a global distributed virtual machine used to realize the concept of ‘network is the computer’. DJM explores coarse-grained parallelism by using the under-utilized workstations on the network, combining the elements of object-oriented technology, distributed computing, World-Wide Web and Java programming. It can run on machines with heterogeneous hardware and software platforms without relinking or recompilation. DJM has two unique features. First, using an original applet helper mechanism, DJM allows machines without any DJM software and of different levels of ‘trust’ to work together. Secondly, DJM has implemented concurrency enhancement mechanisms (one-way message, future and redirected future) to increase the efficiency of method invocation. The prototype of DJM has been implemented and tested under both the Intranet and the Internet environments. Using the workstations from our teaching laboratories, which are already running under normal loading, experimental results show that we can achieve a speedup of about 5–8 times by 14 workstations in a Local Area Network (LAN) environment, and about 4.5 times speedup for eight workstations in a Wide Area Network (WAN) environment. © 1998 John Wiley & Sons, Ltd.     

Performance evaluation of a Windows NT based PC cluster for high performance computing

In recent times the computational power of personal computers has remarkably increased and the use of groups of PCs and workstations, connected by a network and dedicated to parallel computations, is today frequent. Computing clusters are mainly based on UNIX workstations and Linux PCs but, in the last few years, different implementations of message passing systems were made available also for Microsoft Windows. In this work we test the performance of two implementations of MPI for Windows platforms, and we compare the results with those obtained from Linux systems.     

一个基于虚拟机的日志审计和分析系统

SNARE是Linux操作系统的一个日志审计和分析工具,但它容易受到攻击。提出了一个新的方法被用来保护它免受攻击。运用虚拟机监控器的功能,SNARE被移植到运行在虚拟机监控器Xen上的两个虚拟机中,SNARE的两个主要部分——Linux内核补丁和审计后台进程被分隔而分别放入两个被Xen强隔离的虚拟机。Xen提供了两个虚拟机间共享内存的机制,运用这一机制,运行在一个虚拟机上的Linux内核补丁记录并转移审计日志到运行在另一个虚拟机上的审计后台进程。与传统的SNARE相比,新方法使攻击者毁坏或篡改这些日志更加困难。初步的评估表明这个原型是简单而有效的。     

一种具有AAA功能的移动IPv6快速切换方案的研究和实现

和目前WCDMA／GPRS、WLAN网络中的移动性相比，移动IPv6是一种网络层移动性解决方案。具有一定的优势。如垂直切换．但是移动IPv6的切换性能和安全性影响了其商业部署，提出了一种将快速切换和AAA结合起来的机制．并在基于网络处理器的接入路由器和Linux主机上实现了该方案．实验表明，该方案具有较小的切换时延．     

Genetic algorithm for balancing reconfigurable machining lines

We consider the problem of designing a reconfigurable machining line. Such a line is composed of a sequence of workstations performing specific sets of operations. Each workstation is comprised of several identical CNC machines (machining centers). The line is required to satisfy the given precedence order, inclusion, exclusion and accessibility constraints on the given set of operations. Inclusion and exclusion are zoning constraints which oblige or forbid certain operations to be performed on the same workstation. The accessibility constraints imply that each operation has a set of possible part positions under which it can be performed. All the operations performed on the same workstation must have a common part position. Workstation times are computed taking into account processing and setup times for operations and must not exceed a given bound. The number of CNC machines at one workstation is limited, and the total number of machines must be minimized. A genetic algorithm is proposed. This algorithm is based on the permutation representation of solutions. A heuristic decoder is suggested to construct a solution from a permutation, so that the output solution is feasible w.r.t. precedence, accessibility, cycle time, and exclusion constraints. The other constraints are treated with a penalty approach. For a local improvement of solutions, a mixed integer programming model is suggested for an optimal design of workstations if the order of operations is fixed. An experimental evaluation of the proposed GA on large scale test instances is performed.     

Viewing geometric protein structures from inside a CAVE

We have developed general modeling software for a Cave Automatic Virtual Environment (CAVE); one of its applications is modeling 3D protein structures, generating both outside-in and inside-out views of geometric models. An advantage of the CAVE over other virtual environments is that multiple viewers can observe the same scene at the same time and place. Our software is scalable-from high-end virtual environments such as the CAVE, to mid-range immersive desktop systems, down to low-end graphics workstations. In the current configuration, a parallel Silicon Graphics Power Challenge supercomputer architecture performs the computationally intensive construction of surface patches remotely, and sends the results through the I-WAY (Information Wide Area Year) using VBNS (Very-high-Bandwidth Network Systems) to the graphics machines that drive the CAVE and our graphics visualization software, Valvis (Virtual ALpha shapes VISualizer)     

Parallel Application Scheduling on Networks of Workstations

Parallel applications can be executed using the idle computing capacity of workstation clusters. However, it remains unclear how to schedule the processors among different applications most effectively. Processor scheduling algorithms that were successful for shared-memory machines have proven to be inadequate for distributed memory environments due to the high costs of remote memory accesses and redistributing data. We investigate how knowledge of system load and application characteristics can be used in scheduling decisions. We propose a new algorithm based on adaptive equipartitioning, which, by properly exploiting both the information types above, performs better than other nonpreemptive scheduling rules, and nearly as well as idealized versions of preemptive rules (with free preemption). We conclude that the new algorithm is suitable for use in scheduling parallel applications on networks of workstations.     

An environment for developing fault-tolerant software

An environment that supports execution of programs using both N-version programming and recovery blocks in a uniform manner is described. For N-version programming, the system offers an easy and flexible way of specifying the target machines for the separate versions. The basic unit of fault tolerance supported by this system is at the procedure or function level. Each such program unit can be packaged as its own task, and different fault tolerance techniques can subsequently be employed, even within the same application. The environment also allows versions to be written in different programming languages and executed on different machines. This enhances the independence between the different versions, making the fault tolerance techniques more effective. This environment has been developed for use on Unix-based hosts and currently runs on a network of Sun and DEC workstations     

个人计算机和工作站上计算化学软件性能的综合测评

选择Gaussian 98大型计算化学软件包,设计了两组具有代表性的测试算例,在多种个人计算机和工作站硬件、系统软件平台上进行计算性能的综合测试、分析和评价。指出目前高端PC机采用Linux操作系统时性能完全可匹敌最快的工作站,为计算化学研究者选择和构架高性能、价格比的计算机系统提供参考。     

Fault-Tolerant Parallel Scheduling of Tasks on a Heterogeneous High-Performance Workstation Cluster

We propose a new approach, called cluster-based search (CBS), for scheduling large task graphs in parallel on a heterogeneous cluster of workstations connected by a high-speed network (e.g., using an ATM switch at OC-3 speed). The CBS algorithm uses a parallel random neighborhood search which works by refining multiple different initial schedules simultaneously using different workstations. The workstations communicate periodically to exchange their best solutions found thus far in order to direct the search to more promising regions in the search space. Heterogeneity of machines is exploited by the biased partitioning of the search space. The parallel random neighborhood search is fault-tolerant in that the workload of a failed workstation is automatically redistributed to other workstations so that the search can continue. We have implemented the CBS algorithm as a core function of our on-going development of SSI middleware for a Sun workstation cluster.     

Linux虚拟实验环境的搭建及实验设计

虚拟机技术可以在一个物理环境中虚拟出多个独立的逻辑环境,本文利用虚拟机技术这一特点,使用虚拟机软件VMware Workstation为Linux搭建一个虚拟的综合实验环境,并设计了一个可以在该环境上开展的实验项目,方便Linux实验教学的开展和Linux爱好者的学习。     

基于处理能力预约的工作站机群协同调度

本文提出了一种基于处理能力预约的工作站机群协同调度方法,它以一定的处理能力为基础,对参与并行计算的所有工作站进行处理能力的预约,使得并行程序以协调一致的步调得到执行。模拟结果表明,这不仅提高了应用程序所能获得的有效并行计算性能,而且还提高了处理器的利用率,同时它在不同应用环境一的适应性好。     

Transparent process migration: Design alternatives and the sprite implementation

The Sprite operating system allows executing processes to be moved between hosts at any time. We use this process migration mechanism to offload work onto idle machines, and also to evict migrated processes when idle workstations are reclaimed by their owners. Sprite's migration mechanism provides a high degree of transparency both for migrated processes and for users. Idle machines are identified, and eviction is invoked, automatically by daemon processes. On Sprite it takes up to a few hundred milliseconds on SPARCstation 1 workstations to perform a remote exec, whereas evictions typically occur in a few seconds. The pmake program uses remote invocation to invoke tasks concurrently. Compilations commonly obtain speed-up factors in the range of three to six; they are limited primarily by contention for centralized resources such as file servers. CPU-bound tasks such as simulations can make more effective use of idle hosts, obtaining as much as eight-fold speed-up over a period of hours. Process migration has been in regular service for over two years.     

A distributed algorithm for strong bisimulation reduction of state spaces

It is a known problem that state spaces can grow very large, which makes operating on them (including reducing them) difficult because of operational memory shortage. In an attempt to extend the size of the state spaces that can be dealt with, we designed and implemented a bisimulation reduction algorithm for distributed memory settings using message passing communication. By using message passing, the same implementation can be used on both clusters of workstations and large shared memory machines. The algorithm performs reduction of large labeled transition systems modulo strong bisimulation. We justify its correctness and termination and provide an evaluation of the worst-case time and message complexity and some performance data from a prototype implementation. Both theory and practice show that the algorithm scales up with the number of workstations.     

An Introduction to the V-System

A distributed operating system runs on Sun and VAXstation-II workstations connected by an Ethernet. Its distributed kernel provides inexpensive processes and fast interprocess communication.     

A Study of Computerized Offices in Greece: Are Ergonomic Design Requirements Met?

In this study, an investigation was conducted into the extent to which ergonomic requirements for work on computers are met in Greek office workstations. The ergonomic requirements considered were those included in Council Directive 90/270/EEC (1990) of the European Union and the ISO 9241 (1997) standard. 593 office workstations were assessed using an assessment tool consisting of 70 assessment points. The assessment results show that the ergonomic requirements that are independent of the specific characteristics of individual work spaces and environments (e.g., design standards for seats, monitors, and input devices) are adequately met. Ergonomic requirements that should take into consideration the specific characteristics and constraints of individual work content, work spaces, and environments (e.g., requirements dealing with workplace layout, environmental conditions, software, and work organization) are inadequately met. Based on these results, issues are indicated on the effort ergonomists should focus to improve working conditions in computerized offices.