A critical evaluation of PEX

PEX, the PHIGS extension to the X Window System, is evaluated in the context of assumptions inherent in the PHIGS output, modeling, input, user interface, and system environment models. Problems not previously discussed arise when examining PEX this way. The problems not only pertain to the implementation of PEX, but also to implementing a 3-D library in a distributed windowing system in general. The University of Illinois PEX implementation serves as a reference to discuss the solutions proposed     

Combining Graphics and Windowing Standards in the XGKS System

In the past few years we have seen the acceptance of standards for both two and three dimensional computer graphics. Also during this time, the workstation community has converged on a common windowing system. This paper discusses the problems encountered in implementing graphics standards such as GKS and PHIGS PLUS within the X Window System environment.     

A PHIGS-based graphics input interface for spatial-mechanism design

A graphics preprocessor that interactively assists in the definition of spatial-mechanism problems is described. Methods of depth cueing and six-degree-of-freedom data entry are presented. To achieve graphics device independence, the proposed graphics standard PHIGS (Programmer's Hierarchical Interactive Graphics System) has been used. Examples of applications include generation of input commands for the Integrated Mechanisms Program (IMP) and generation of input for spatial-mechanism synthesis routines     

Developing Java-AWT thin-client applications for limited devices

Developing software for personal wireless devices (PWDs) requires new methods and tools that address the restrictions introduced by these devices' mobile nature. The thin-client applications for limited devices (TCPTE) framework supports the development of thin-client applications for mobile devices with limited resources. Using TCPTE, we can execute Java applications on a server and display their AWT interfaces on a remote client. TCPTE combines the advantages of thin-client computing with the richness of client-server graphical interfaces and lets programmers develop applications for PWDs using the same processes and tools they typically use for desktop applications.     

基于曙光5000并行机的远程并行调试器

并行调试对并行程序开发非常重要,然而传统的远程并行调试方式是采用登录(telnet)命令通过命令行的文本界面进行,非常繁杂。本文介绍了为曙光3000系统设计实现的远程并行调试器RPB(Remote Parallel Debugger)。RPB实现了完全并行调试等功能,并且具备图形用户界面,用户界面采用Java语言和Swing工具包实现,具备平台独立的特点。RPB采用客户端/服务器模式,客户端和服务器之间的通信采用当今流行的CORBA中间件技术。RPB支持通过局域网或广域网远程调试并行机上的程序,屏蔽了客户平台的差异和并行机地理位置上的差异,因而大大提高了并行机的好用性。     

Migrating legacy scientific applications towards CORBA‐based client–server architectures

A distributed object is a reusable, self‐contained piece of software that cooperates with other objects on the same machine or across a network in a plug‐and‐play fashion via a well‐defined interface. The Numerical Propulsion System Simulation (NPSS) attempts to provide a collaborative aircraft engine design and simulation environment based on this concept. Many scientific applications in aerodynamics and solid mechanics are written in Fortran. Refitting this legacy Fortran code with distributed objects can increase code reusability. In this paper, we focus on the novel use of a remote variable scheme to help programmers migrate the Fortran code towards a client–server architecture. This scheme gives the client the capability of accessing variables at the server site and makes it easier for programmers to couple component engine code. Through the operator overloading features in C++, remote variables can be used in much the same way as traditional variables. The remote variable scheme adopts the lazy update approach and the prefetch method. Preliminary performance evaluation shows that communication overhead can be greatly reduced. Copyright © 2001 John Wiley & Sons, Ltd.     

基于机群操作系统的并行调试器

并行调试工具的设计，是并行计算环境工具研究开发中的一个突出难点。介绍了一个在曙光3000上实现的并行调试器DCDB3．0。该调试器是未来曙光4000机群操作系统的一部分，是曙光3000上的第1个可运行版本，采用典型的客户／服务器模式。客户端的用户界面可将冗繁的调试信息与操作可视化。客户端可以远离提供服务的大型机，其远程通信依赖的是机群操作系统中的DRPC和任务管理，前者提供远程方法调用，后者使得客户端能够在服务器上启动相应的任务。DCDB3．0的服务器端负责处理调试任务和同客户端进行信息交互。DCDB3．0的功能具有可扩放性，使得可以在此平台上研究一些高级并行调试技术的实现。改进了已有的方式，实现了重放技术，并计划进一步添加其他高级并行调试技术。     

Xconf: A Network-Based Image Conferencing System

People often need to get together to share and discuss small amounts of image and textual data, but this is difficult when they are not located in the same place. One solution to this problem is Xconf, a multimedia computer conferencing groupware tool using existing national and international networks (the Internet). Simultaneous conferencing supports real-time interaction between multiple remote computer displays. Xconf multimedia may include conversational text, images, pointers to objects in images, and group execution of programs. Conferencing may take place with or without images. Interaction is tightly coupled with all users aware of global changes to the shared session and alternatively, individuals may monitor a specific subgroup of other users to concentrate on what they are discussing. Collaborative groups who have access to both computer networks and networked based X-Window System graphics displays can participate in a conference. Xconf is an X-Window "client" program which provides multimedia conferencing support for a group of X-Window displays. Because it is centralized, no software other than the standard X Window System is required on any of the participants display systems. Key data structures and algorithms for image conferencing are present.     

远程调试的设计与实现

一般情况下,调试器与被调试程序（目标程序）运行在同一个计算机系统环境中,但是,在实时系统、内核调试及一些Ｃｌｉｅｎｔ／Ｓｅｒｖｅｒ系统等情况下,调试器不能运行在目标程序运行的环境中,此时有效的解决方法就是实施远程调试（Ｒｅｍｏｔｅ ｄｅｂｕｇｇｉｎｇ）。远程调试系统由本地调试器、远程调试服务器以及远程调试通讯协议组成。该文详细讨论这三部分的设计与实现,并介绍一个自行设计的基于远程调试的并行调试器。     

PHIGS: A Standard, Dynamic, Interactive Graphics Interface

The Programmer's Hierarchical Interactive Graphics System (PHIGS) is a draft standard for computer graphics programming. PHIGS is useful for applications that manipulate complex displays of 2D or 3D data in a highly interactive environment. This is done through the hierarchical data organization and flexible editing capabilities provided in PHIGS. This article describes the goals and underlying model of PHIGS, reviews its capabilities, and provides some brief application examples. The similarities and differences of PHIGS and GKS are discussed.     

An execution profiler for window-oriented applications

Execution profiles are important in analyzing the performance of computer programs on a given computer system. However, accurate and complete profiles are difficult to arrive at for programs that follow the client-server model of computing, as in the popular X Window System. In X Window applications, considerable computation is invoked at the display server and this computation is an important part of the overall execution profile. The profiler presented in this paper generates meaningful profiles for X Window applications by estimating the time spent in servicing the messages in the display server. The central idea is to analyze a protocol-level trace of the interaction between the application and the display server and thereby construct an execution profile from the trace and a set of metrics about the target display server. Experience using the profiler for examining bottlenecks is presented.     

An Implementer's View of PHIGS

The Programmer's Hierarchical Interactive Graphics System (PHIGS) specifies an interface for programming device-independent computer graphics applications. After a brief review of PHIGS concepts, an experimental environment used to study and evaluate the proposed standard is presented. The basic structure and distribution of function in this PHIGS implementation is discussed. We describe the architecture of a device-independent environment designed to realize the performance essential to the adequate functioning of a PHIGS implementation. The results presented emphasize the PHIGS output model. Full utilization of workstation processing capabilities, minimization of host/workstation interaction and efficient data management are key to our implementation.     

The Priority Tree, a HL/HSR Approach for PHIGS

The Programmer's Hierarchical Interactive Grahics System (PHIGS) specifies an interface for programming device-independent computer graphics applications. PHIGS provides a powerful data grouping mechanism, called the PHIGS structure, that may be used to model the geometry of 3D objects. Hidden Line/Hidden Surface Removal (HL/HSR) is a required process to produce realistic solid views of the modeled objects. Modeling clip is an essential process for viewing a clipped portion of the modeled objects. A technique is presented that provides HL/HSR and modeling clip as added utilities to PHIGS. The technique is based on the Binary Space Partitioning (BSP) tree (sometimes called priority tree), and involves a back to front sorting of the primitives of a PHIGS structure network to another PHIGS structure. Modeling clip is achieved by limiting the sorting to those primitives in a specified clip ping region of the object space. The resulting structure when displayed on a raster device produces a realistic view of the possibly clipped object that was originally modeled by the PHIGS structure network.     

A short recipe for seashell synthesis

Several artistic examples of seashell-like forms produced on a graphics supercomputer are provided. The shapes were created using a simple graphics primitive and rendered using lighting and shading facilities of 3-D extensions to X Windows or the PHIGS+ proposed standard. It is expected that the techniques, equations, and systems will provide useful tools and stimulate future studies in the graphics characterization of morphologically rich spiral shapes produced by relatively simple generating formulas     

Virtual network computing

VNC is an ultra thin client system based on a simple display protocol that is platform independent. It achieves mobile computing without requiring the user to carry any hardware. VNC provides access to home computing environments from anywhere in the world, on whatever computing infrastructure happens to be available-including, for example, public Web browsing terminals in airports. In addition, VNC allows a single desktop to be accessed from several places simultaneously, thus supporting application sharing in the style of computer supported cooperative work (CSCW). The technology underlying VNC is a simple remote display protocol. It is the simplicity of this protocol that makes VNC so powerful. Unlike other remote display protocols such as the X Window System and Citrix's ICA, the VNC protocol is totally independent of operating system, windowing system, and applications. The VNC system is freely available for download from the ORL Web site at http://www.orl.co.uk/vnc/. We begin the article by summarizing the evolution of VNC from our work on thin client architectures. We then describe the structure of the VNC protocol, and conclude by discussing the ways we use VNC technology now and how it may evolve further as new clients and servers are developed     

Top Draw: A Structure Network Visualiser for PHIGS

The Programmer's Hierarchical Interactive Graphics System (PHIGS) is an International Standard for computer graphics. PHIGS provides a flexible mechanism for creating hierarchical models from collections of directed acyclic graphs known as 'structure networks'. In practice, the combination of powerful data structuring facilities and the ability to dynamically edit structure networks can lead to a potential complexity which makes models difficult to manage and maintain reliably.
This paper presents TopDraw , a portable programming tool for visualising PHIGS structure networks, by automatically documenting their topology using diagrams. Drawing tidy representations of graphs algorithmically is a difficult problem, and most existing systems are large, complex and speciallsed The alternative approach taken in TopDraw is to use a fast, straightforward algorithm supplemented when necessary by an interactive 'tidief. A novel feature of TopDraw is that the diagrams it produces are themselves PHIGS structures, which the application may edit and manipdate as required. TopDraw is a component of the PHIGS Toolkit , an emerging set of portable integrated tools for PHIGS environments.     

Remote database access in the distributed computing environment

This paper describes the design, implementation and testing of a set of software modules that are used for remote database access in a distributed computing environment. The goal of our research and development is to implement a client server model using Structured Query Language (SQL) functions in the Open Software Foundation's (OSF) distributed computing environment (DCE). This design is compared with another which simply uses the sockets application programming interface (API), running over the transmission control protocol/internet protocol (TCP/IP), and is implemented in subroutines that act similar to the remote procedure call (RPC) generated stub code. The prototypes for the remote SQL access project are implemented using an IBM RISC System/6000 (the client) running the AIX operating system and an IBM AS/400 (the server) running the OS/400 operating system. We selected the AS/400 for its database abilities, and the RISC System/6000 since the DCE software is available for it.     

基于Windows的远程文件备份系统的设计与实现

该文提出并实现了一种基于Windows的远程文件备份系统。该系统通过改进的差异算法和快照技术,有效地利用了网络带宽,实现高效,快速的文件同步;采用epoll机制,使服务器能够处理大规模的用户访问;对于文件进行归档管理。该系统实现了对本地数据的远程备份,为个人用户的数据安全提供了一套合理的远程数据备份方案。     

X Window/Motif编程中颜色问题的探讨

X Window/Motif是计算机工作站、大型机和采用 UNIX操作系统的微机上最主要的窗口系统 ,但我们大多数人对其编程甚至其系统都不是十分熟悉。 XWindow/Motif是一个十分复杂的系统 ,文章着重讲述了在开发 X Window/Motif界面应用程序中如何定制及使用颜色 ,并给出了一个实用程序的介绍。另外还提出了一种自定义状态条的方法