General-purpose Language Research Articles

System structure for parallel logic programming

A system structure supporting parallel processing in general and parallel logic programming and expert system applications in particular is described. It is not based on special hardware but has rather been designed as an evolutionary extension to most existing machine architectures. It is aimed at parallel processing support for e.g. PROLOG as well as for expert system (shells) implemented in a general purpose language. A layered structure consisting of an extended machine interface and a macro language is chosen to support a range of various applications.

A design methodology for synthesizing parallel algorithms and architectures

In this paper, a design methodology for synthesizing efficient parallel algorithms and VLSI architectures is presented. A design process starts with a problem definition specified in the parallel programming language Crystal and is followed by a series of program transformations in Crystal, each aiming at optimizing the target design for a specific purpose. To illustrate the design methodology, a set of design methods for deriving systolic algorithms and architectures is given and the use of these methods in the design of a dynamic programming solver is described. The design methodology, together with this particular set of design methods, can be viewed as a general theory of systolic designs (or multidimensional pipelines). The fact that Crystal is a general purpose language for parallel programming allows new design methods and synthesis techniques, properties and theorems about problems in specific application domains, and new insights into any given problem to be integrated readily within the existing design framework.

Beyond desire: Pascal implementations of direct-executing simulation languages

Two new simulation languages, DESIRE P and DESCTOP, combine interpretation of the experiment protocol with fast compilation of the model differential equations and thus execute directly on a typed RUN command. Simulations run at about FORTRAN 77 speed. While earlier languages of this type (MICRODARE and DESIRE V3) were implemented in assembly language, both new systems are written in PASCAL except for FORTRAN integration routines and a small machine-language interface, so that the code was readily ported from the PDP-11 to the VAX. DESIRE P incorporates a new one-pass compiler and some precompiler syntax checking. DESCTOP is a general-purpose workstation language with complex arithmetic, matrix transformations, fast Fourier transforms, true procedures, and structured programming with automatic prettyprinting. Like DESIRE V3, both new languages permit convenient screen editing and contain operating-system commands and command procedures as a language subset. On the VAX, both languages support simulation with 100 or more state variables and Tektronix color graphics. An IBM PC/XT/AT version also exists.

Transition from Coral to Ada programming

The programming language Coral 66 has a large following in the UK as a general-purpose computer language, especially in the embedded computer application area. The Ada programming language is destined to become an international standard language and was designed to satisfy the needs of the same application area as Coral 66. A change from programmingn in Coral to Ada is inevitable in many future projects, especially those which need large teams and which have a requirement for long term maintenance. The major features of the two languages are compared in an attempt to dispel some of the fears which seem to surround the transition from Coral 66 to Ada.

Programming Denotational Semantics II

The Denotational Semantics of a small programming language is coded into Algol-68 to give an interpreter. The Semantics incorporates many of the notions of Standard Semantics including declarations, declaration continuations, final answers and stores or memory which are used to define block structuring, output and parameterless procedures. This extends work previously reported1. The coding in Algol-68 is quite straightforward and the result is a type checked and executable semantics which is as readable as the original semantics to one familiar with Algol-68. No special software is needed other than a compiler for the general purpose language Algol-68.

Implications of the ADA® environment for simulation studies

Ada packages to support event and process oriented simulation have been developed at Texas A&M University. These packages include standard Facilities such as queue handling, random number generation, automatic statistics collection and simulation control. This paper provides an overview of the system facilities followed by an evaluation of the strengths and weaknesses of Ada as an implementation language for simulation software. Based on our experience Ada has appeal as a general purpose language which can be integrated into larger systems. It is portable among various computer architectures, it provides a rich base of constructs in which to implement models, and offers promise in terms of execution on parallel architectures.

How control languages should be designed, with an integrated example design

For 20 years, digital process control applications have been programmed and “configured” in a variety of general-purpose languages and special-purpose packages. During this time, some advances have been made, notably the concepts of application languages based on established diagrammatic documentation techniques, such as the block diagram or the ladder diagram. But these languages have been incomplete; much of the control application has required general-purpose languages not reflecting any particular application view and, therefore, requiring a lot of user reinvention. In all of this effort, no one in the computer or process control field has attempted to formalize a concept of language quality for human use. This paper presents a listing of the weaknesses of existing general-purpose and application languages, and outlines principles for overcoming these weaknesses. While the references develop previously shown techniques for demonstrating reduced human programming and analysis effort through use of specialized language features, the validation of an entire language, in these terms, is beyond the scope of this paper. Instead, we will show a videotape demonstrating the impact and range of an illustrative example control language, designed according to the discussed principles, through four quite different application examples: 1. 1. A Two-Loop Cascade Startup 2. 2. A Subsystem I/O Variables Definition 3. 3. A Major Plant Startup 4. 4. A Complex Multi-Unit Continuous Control System From these examples, the overall power and characteristics of the example language and the underlying techniques should be apparent.

Exploiting Domain Knowledge in IC Cell Layout

This article describes a knowledge-based expert system, Talib, whose domain of expertise is in the cell layout phase of the IC design task. It applies Al techniques and has been used to design IC layouts in the circuit range of four to 86 transistors. The system is implemented in OPS5, a general-purpose rule-based language. Talib accepts as input the schematic of the proposed circuit along with the description of the cell layout boundary, and produces as output the description of the mask geometry in CalTech Intermediate Form. The cell layout problem is based on a single metal, single polysilicon, NMOS process. It is further constrained to be in the framework of Manhattan geometry, hence only orthogonal lines are used.

EMDISP: A visual display system with digital and analogue sampling

EMDISP provides general-purpose assembly language routines that can be called from higher level languages to produce specific application programs for experiments involving visual displays, manual responses, and analogue sampling (e.g., eye movement recording). The display system assumes the use of fast-phosphor oscilloscopes driven by 12-bit digital-to-analogue converters (DACs) to produce point-by-point displays. Within these limitations, EMDISP offers a flexible and efficient method of generating displays, in which elements of a complex display are defined as separate “pictures” and are controlled independently. High-level control of digital and analogue sampling are provided, enabling interactions between the contents of the display and analogue and digital inputs.

Processes, Tasks, and Monitors: A Comparative Study of Concurrent Programming Primitives

Three notations for concurrent programming are compared, namely CSP, Ada, and monitors. CSP is an experimental language for exploring structuring concepts in concurrent programming. Ada is a general-purpose language with concurrent programming facilities. Monitors are a construct for managing access by concurrent processes to shared resources. We start by comparing "lower-level" communication, synchronization, and nondeterminism in CSP and Ada and then examine "higher-level" module interface properties of Ada tasks and monitors.

Comparison of database interfaces for application programming

The historical evolution of interfaces to databases at the application programming level is analyzed. Emphasis is put on aspects of the data manipulation operations rather than on the data model that they address. Four phases are distinguished in this evolution: “call” interfaces, simple language extensions, non-procedural languages embedded in general purpose languages, and integrated languages. The evolution is explained in terms of the growing needs for more reliable programs written in high level languages, for which programmer efficiency is more important than machine efficiency.

The contraction of control implementations

The implementation of a high level language which provides higher control forms such as concurrency and coroutines along with the more traditional recursive procedures is obligated to support all control forms in a reasonably efficient manner. In particular, the implementation of a general purpose language (such as Simula or Ada) should contract gracefully into a scheme incurring overhead approximately the same amount as a simple stack when presented with programs which employ control forms no more general than recursive procedures. This study is a quantitative investigation into the contraction of implementations capable of supporting higher control forms into an environment in which recursive procedures are the most complex control form. A technique called the stack-heap is shown to contract most fully.

Improved file handling for discrete-event models with event cancellation

Discrete-event models written in general-purpose simulation languages often run slowly because of the ways in which these languages file and search for events. For example, files may regularly be searched starting from the wrong end, newly created events may be assumed to occur later than events already filed, next events for particular entities may not be directly accessible, and events that must be cancelled may re quire extensive searches. Improved filing procedures include automatic selection of backward or forward searching, main tenance of a matrix of next events for particular entities, and saving of events in a FIFO file until their occurrence times near. In the case of a GASP IV model of electrical power generating systems, improving file handling reduced its run time by an order of magnitude. This model involves frequent creation and cancellation of events as units are turned on and off. Furthermore, the operator must select the particular units to be started or removed from operation on the basis of cost and other factors.

PICAP–A System Approach to Image Processing

Image processing puts heavy demands on computational speed and storage space. The PICAP system of Linkoping University has been designed to meet these demands in an interactive image processing environment, utilizing state-of-the-art hardware and software components. PICAP is a multiuser system, and computational speed is achieved through parallelism at both global and local levels. A virtual image memory alleviates the problem of storage space. The users can invoke the PICAP facilities by means of a menu-based language or a general-purpose high-level language. The modular and open-ended architecture of PICAP makes it highly adaptive to future advances in both hardware and software technologies.

Josef, programming for everybody

The author believes that everybody should be introduced to programming but that standard general purpose languages are not suitable for this purpose, mainly because they do not provide an environment offering natural problems. Another characteristic which makes them unsuitable for the purpose is that they are all more or less burdened by restrictions imposed by legitimate concerns of professional programmers with security and economical aspects of programming. This paper briefly considers the general features that a programming language intended for the introduction of an average non-programmer should have and describes some aspects of one such language developed by the author.

The Document Interchange Architecture: A member of a family of architectures in the SNA environment

DIA, although oriented to an office systems application, can be a general-purpose language used to interchange information and control requests among applications in a distributed processing environment. DIA is defined to be both semantically and syntactically extendable in order to have a long life.

Automatic encoding of clinical narrative

An experiment in the automatic encoding of English-language medical data is described. The encoding program has two stages. First, the free-text input is parsed and the information is arranged in a tabular format by a general-purpose natural language processor developed at New York University. Then a simple code-dependent subprogram assigns numerical values to the entries on the basis of the positions the input words occupy in the information format. Results of a blind test of the encoding program using the code employed at Roswell Park Memorial Institute for earliest symptoms of head-neck cancer are presented.

Simulation of Manufacturing Systems Using SIMAN

This paper discusses the concepts and methods for simulating manufacturing systems using the new SIMAN simulation language. SIMAN is a powerful general purpose language which incorporates a number of special purpose features which are specifically designed to enhance the modeling of manufacturing systems. These features greatly simplify the task of modeling the material handling component of a manufacturing system. The modeling concepts included in SIMAN are illustrated by several small example models. In addition, a recent application of SIMAN to model a manufacturing system at an industrial plant is discussed. This application involved a comparison of proposed group technology layouts against the existing conventional layout in the plant.

Josef, the robot

Computers cannot be properly understood without at least an elementary exposure to programming. Many teachers would reject this proposal on the grounds that for many people programming is too difficult and uninteresting. This objection is probably correct if we imply that programming should be introduced in a general purpose programming language. Its validity becomes questionable if the vehicle is a special programming language which puts the student into a natural environment, familiar to every ordinary person. The LOGO system is a well known example of such a natural environment. This article presents a related language called Josef which is used to program a robot moving on the map of a computer terminal. The distinguishing features of Josef are: (a) Extensibility of built-in vocabulary: (b) Possibility of fully top-down approach to the solution of large problems; (c) Similarity to general purpose languages in terms of concepts available in the language and the syntax used to express them: (d) Ability to work on ordinary computer terminals. The larger part of the article attempts to present the general philosophy of the language on a few programming examples of medium complexity.

A two-list synchronization procedure for discrete event simulation

The traditional mechanism for maintaining a list of pending events in a discrete event simulation is the simple linked list. However, in large scale simulations this list often becomes cumbersome to maintain since the number of pending events may become quite large. As a result, the execution time required by the simple linked list is often a significant portion of total simulation time. Several papers have been published suggesting improved synchronization procedures. The most efficient procedures reported are the time-indexed procedure and the two-level procedure. Both methodologies are much more efficient than simple linked lists; however, neither has been adopted by a general purpose simulation language. Further, both procedures require external parameter definition, which is a major handicap to their adoption by a general purpose language. This paper introduces a new sychronization procedure, the two-list procedure, which is much faster than simple linked lists for large pending event files. This procedure was designed for implementation in Fortran, and properly implemented it is transparent to the user. Thus it is ideal for adoption by general purpose simulation languages.