Implementing Ada Exceptions

Can exceptions be implemented for Ada without imposing overhead on normal execution? Yes, as long as certain rules are followed.     

Ada95语言评述

Ａｄａ９５语言是在Ａｄａ８３基础上修订而成的，它几乎提供了现代程序设计范型及程序设计实践所需要的一切设施，它可以支持面向对象的程序设计、大型程序设计、实时与并行程序设计等等。     

Ada95与面向对象的程序设计

本文首先分析了Ａｄａ８３对面向对象的程序设计的支持特征，然后对Ａｄａ９５在Ａｄａ８３的基础上所新增加的面向对象设施进行了详细的介绍与讨论。     

Ada95编译系统中多平台技术的研究

支持多语种、多平台是当前编译技术的发展趋势,它适应了当前计算机系统迅猛更新的需要。文中提出了一个适用于不同计算机平台的多平台Ada95编译系统的模型,在此基础上讨论了Ada95编译系统中多平台支持的三个关键技术:平台配置机制、运行库多平台支持技术和多平台代码生成支持策略,并描述了相应的设计与实现方法。     

Ada95分布系统模型的分析

本文详细分析了Ada95分布系统模型的语义,重点探讨了分布单元的构成、通信和库单元分类编译指示,最后给出了网络应用的例子。     

Ada95保护对象与面向数据的同步

本文详细讨论了Ａｄａ保护对象机制，分析其应用并将之与其它有关设施进行了分析与比较。     

类和对象的Ada95代码的自动生成

本文提出了一种自对象类的用户描述自动生成Ａｄａ９５代码的方法。     

CSPL: an Ada95-like, Unix-based process environment

The paper presents a new process-centered environment called “concurrent software process language” (CSPL). CSPL takes a unique and innovative approach to integrate the object-oriented Ada95-like syntax (for its modeling power) with Unix shell semantics (for its enactment capability) in a software process language. The paper depicts the following new CSPL features: (1) object orientation, (2) multirole and multiuser, and (3) unified object modeling. Language constructs specially designed for software process such as work assignment statement, communication-related statements, role unit, tool unit, relation unit and so on, are, respectively, described. The related work of this diversified field is also surveyed in some depth. The CSPL environment prototype has been built. A CSPL process program for the IEEE Software Process Modeling Example Problem has been developed and enacted to demonstrate the capabilities of this environment     

Ada95层次库结构与大型软件开发

Ａｄａ９５提出了层次库和后扩库单元的概念提供了相应的设施，对Ａｄａ８３的分别编译设施与可见性规则进行了扩充。本文对层次库的概念与设施进行了详细的介绍、分析与讨论。     

Dynamic synchrony among atomic actions

Synchrony continues to be an important concern in concurrent programming. Existing languages and models have introduced a great diversity of constructs for expressing and managing synchronization among sequential processes or atomic actions. The authors put forth a model in which synchrony is viewed as a relation among atomic actions, a relation which may evolve with time. The model is shown to be convenient for expressing formally the semantics of synchrony as it appears in many of the languages and models proposed to date. Among such models Swarm is singled out for its use of dynamic synchrony. The Swarm notation is briefly reviewed. A new concurrent algorithm for the leader election problem illustrates the use of dynamic synchrony in Swarm     

State restoration in Ada 95: a portable approach to supporting software fault tolerance

Studies indicate that techniques for tolerating hardware faults are so effective that software design errors are the leading cause of all faults encountered. To handle these unanticipated software faults, two main approaches have been proposed: N-version programming and recovery blocks. Both are based on the concept of design diversity: the assumption that different designs will exhibit different faults (if any) for the same inputs and will, therefore, provide alternatives for each other. Both approaches have advantages, but this paper focuses upon recovery blocks; specifically, the requirement to save and restore application state. Judicious saving of state has been described as “checkpointing” for over a decade. Using the object-oriented features of the revised Ada language (Ada 95) – a language widely used in this domain – we present three portable implementations of a checkpointing facility and discuss the trade-offs offered by each. Results of the implementation of these mechanisms are used to highlight both the strengths and weaknesses of some of the object-oriented features of Ada. We then show a reusable implementation of recovery blocks illustrating the checkpointing schemes. A performance analysis is made and measurements are presented in support of the analysis.     

关于Ada95变体部分等语法的修正意见

本文指出了Ａｄａ９５ 参考手册中记录变体部分、记录聚集、分情形语句与异常处理段等语法描述中存在的问题，并分别给出了它们的修正方案。     

Ada并发程序设计

<正> 该书1984年出版,作者系美国贝尔实验室的Narain Gehani。该书从公认的第一个提供高级通用并发程序设计设施的Ada语言着手,全面地介绍了Ada语言中的并发程序设计设施,以及如何有效利用这些设施编写并发程序;概述了在其它语言的并发程序设计设施;讨论了并发程序设计中的一些细节问题;书末还附录了Ada顺序程序设计的概要。目前,各种大小的并行计算机及操作系统都已相继问世并投入实际使用。并行处理将是今后几年计算机工程和应用的发展方向之一,也是新一代计算机的核心技术之一。但是如果缺乏高度并行的程序设计语言和方法,将会给广泛的应用带来很大障碍,这已引起计算机各     

Implementing the new Ada 2005 timing event and execution time control features on the AVR32 architecture

This paper describes how the new Ada 2005 timing event and execution time control features were implemented for the GNAT bare-board Ravenscar run-time environment on the Atmel AVR32 architecture. High accuracy for execution time measurement was achieved by accounting for the effects of interrupts and executing entries by proxy. The implementation of timing events was streamlined by using a single alarm mechanism both for timing events and waking up tasks. Test results on the overhead and accuracy of the implemented features are presented. While the implementation is for the AVR32, it may serve as a blueprint for implementations on other architectures. It is also discussed how the presented design could be transferred to other systems such as C/POSIX and RTSJ.     

Ada并发程序设计

<正> 死锁,不一定的时序和不一定的轮询都是并发程序设计问题,这些问题通常对顺序程序设计不感兴趣,甚至无关。这些问题发生在并发程序设计之中,而不管程序设计语言提供了什么样的并发程序设计设施。但是,程序设计语言中的并发设施的精确特性对这些问题的严重性与经常性确有影响。本章讨论三个并发程序设计问题:死锁,程序中的最大并发特性,以及Ada中的轮询偏向。 1.死锁当程序中的一个或多个任务被永远阻塞时,死锁就发生了,因为需求不能满足。在一些任务中,死锁会成为某些任务中的一种     

Critical races in Ada programs

It is noted that critical races in concurrent Ada programs are an insidious source of system errors, and that the Ada language does not have concurrency features to ease the development of critical race-free programs. The authors illustrate this using the CRF language, which extends the Ada language by the addition of a powerful caller selection mechanism. It is this facility that implements a discriminatory mutual exclusion (dimutex) construct, an important feature for building less critical race-prone programs. The MLog language supports the CRF caller selection mechanisms; thus it is convenient as a rapid-prototyping platform. A design method for systematically converting CRF designs into Ada designs is presented. The method uses a mixture of mechanical and creative transformations that are guaranteed not to introduce critical races. D. Helmbold and D. Luckham's (1985) gas-station example is used to illustrate the various approaches to applying the design method     

Concurrency in Ada and multicomputers

Implementation of Ada's parallel tasks on a multicomputer architecture requires additional communication and naming overhead because tasks can operate on shared data via global variables and pointers. This increases the complexity of implementing Ada and has a negative impact on program understandability.