Gopal Gupta

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Gopal Gupta

Monash University

Mats Carlsson

Swedish Institute of Computer Science

Mats Carlsson

RISE Research Institutes of Sweden (RISE)

Khayri Ali

Manuel Carro

Universidad Politécnica de Madrid

Petros Kefalas

International Faculty of the University of Sheffield, City College - Thessaloniki

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Papers by Gopal Gupta

And-Or Parallel Prolog: A Recomputation Based Approach

New Generation Computing, 1993

We argue that in order to exploit both Independent And-and Or-parallelism in Prolog programs ther... more We argue that in order to exploit both Independent And-and Or-parallelism in Prolog programs there is advantage in recomputing some of the independent goals, as opposed to all their solutions being reused. We present an abstract model, called the Composition-tree, for representing and-or parallelism in Prolog programs. The Composition-tree closely mirrors sequential Prolog execution by recomputing some independent goals rather than fully re-using them. We also outline two environment representation techniques for And-Or parallel execution offull Prolog based on the Composition-tree model abstraction. We argue that these techniques have advantages over earlier proposals for exploiting and-or parallelism in Prolog.

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Analysis of Or-parallel execution models

ACM Transactions on Programming Languages and Systems, 1993

We discuss fundamental limitations of or-parallel execution models of nondeterministic programmin... more We discuss fundamental limitations of or-parallel execution models of nondeterministic programming languages. Or-parallelism corresponds to executing the di erent nondeterministic computational paths in parallel. A natural way to represent the state of (parallel) execution of a nondeterministic program is by means of an or-parallel tree. We identify three important criteria that underlie the design of or-parallel implementations based upon the or-parallel tree: constant-time access to variables, constant-time task creation, and constant-time task switching, where the term`constant-time' means that the time for these operations is independent of the number of nodes in the or-parallel tree, as well as the size of each node. We prove that all three criteria cannot be simultaneously satis ed by any or-parallel execution model based on a nite number of processors but unbounded memory. We discuss in detail the application of our result to the class of logic programming languages, and show how our result can serve as a useful way to categorize the various or-parallel methods proposed in this eld. We also discuss the suitability of di erent or-parallel implementation strategies for di erent parallel architectures. y This paper generalizes and expands the results in our paper, \Criteria for Or-Parallel Execution Models of Logic Programs," in

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Parallel Execution of Prolog Programs: A Survey

ACM Transactions on Programming Languages and Systems, 1995

Since the early days of logic programming, researchers in the field realized the potential for ex... more Since the early days of logic programming, researchers in the field realized the potential for exploitation of parallelism present in the execution of logic programs. Their high-level nature, the presence of non-determinism, and their referential transparency, among other characteristics, make logic programs interesting candidates for obtaining speedups through parallel execution. At the same time, the fact that the typical applications of logic programming frequently involve irregular computations, make heavy use of dynamic data structures with logical variables, and involve search and speculation, makes the techniques used in the corresponding parallelizing compilers and run-time systems potentially interesting even outside the field. The objective of this paper is to provide a comprehensive survey of the issues arising in parallel execution of logic programming languages along with the most relevant approaches explored to date in the field. Focus is mostly given to the challenges emerging from the parallel execution of Prolog programs. The paper describes the major techniques used for shared memory implementation of Or-parallelism, Andparallelism, and combinations of the two. We also explore some related issues, such as memory management, compile-time analysis, and execution visualization.

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Towards a Universal Maths Conversion Library

The study of Mathematics and Sciences have always been a difficult problem for blind students esp... more The study of Mathematics and Sciences have always been a difficult problem for blind students especially because of the complexity of Braille mathematical notations. Various projects developed converters allowing people to translate a formula from mainstream notations (like LATEX or MathML) to Braille notations and vice versa. Today a new generation of tools aims at facilitating the understanding of the formulas by blind users, and the communication between sighted and Braille users. The project of Universal Maths Conversion Library is born from the decision of 6 organisations both American and European to join their efforts in that field.

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ACE: a high-performance parallel Prolog system

In recent years a lot of research has been invested in parallel processing of numerical applicati... more In recent years a lot of research has been invested in parallel processing of numerical applications. However, parallel processing of Symbolic and AI applications has received less attention. This paper presents a system for parallel symbolic computing, named ACE, based on the logic programming paradigm. ACE is a computational model for the full Prolog language, capable of exploiting Or-parallelism and Independent And-parallelism. In this paper we focus on the implementation of the and-parallel part of the ACE system (called &ACE) on a shared memory multiprocessor, describing its organization, some optimizations, and presenting some performance figures, proving the ability of &ACE to efficiently exploit parallelism.>

A constraint-based approach for specification and verification of real-time systems

We develop a general constraint logic programming (CLP) based framework for specification and ver... more We develop a general constraint logic programming (CLP) based framework for specification and verification of real-time systems. Our framework is based on the notion of timed automata that have traditionally been used for specihing real-time systems. In our framework, a user models the ordering of real-time events as the grammar of a language accepted by a timed automata, the real-time constraints on these events are then captured as denotations of the grammar productions specijied by the usel: The grammar can be speciJied as a Definite Clause Grammar (DCG), while the denotations can be speccped in constraint logic. The resulting specijication can hence be regarded as a constraint logic program (CLP), and is executable. Many interesting properties of the real-time system can be verc3ed by posing appropriate queries to this CLP program. A major advantage of our approach is that it is constructive in nature, i.e., it can be used for computing the conditions under which a property will holdfor a given real-time system. Our framework also suggests new types of formalisms that we call Constraint Automata and Timed Push-down Automata.

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UMA: a system for universal mathematics accessibility

We describe the UMA system, a system developed under a multi-institution collaboration for making... more We describe the UMA system, a system developed under a multi-institution collaboration for making mathematics universally accessible. The UMA system includes translators that freely inter-convert mathematical documents transcribed in formats used by unsighted individual (Nemeth, Marburg) to those used by sighted individuals (LaTeX, Math-ML, OpenMath) and vice versa. The UMA system also includes notation-independent tools for aural navigation of mathematics.

Reading and writing mathematics: the MAVIS project

One of the greatest challenges to the visually impaired student in science and mathematics disci-... more

Navigation of HTML tables, frames, and XML fragments

In this paper, we provide a progress report on the development of technology to support the non-v... more

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Parallel execution of prolog programs: a survey

ACM Transactions on Programming Languages and Systems, 2001

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A domain specific language framework for non-visual browsing of complex HTML structures

G. Gupta Dept. Computer Science University of Texas at Dallas Richardson, TX 75083 [email protected].... more

User authorization based on keystroke latencies

Communications of The ACM, 1990

Identity authentication based on keystroke latencies

Communications of The ACM, 1990

Since inexpensive computers possessing sophisticated graphics were introduced in the late 1970s, ... more Since inexpensive computers possessing sophisticated graphics were introduced in the late 1970s, program development research has focused on syntax-directed editors that are based on the grammars of their underlying languages. The system presented here automatically generates object-oriented, syntax-directed editors for visual languages, which are described by a family of editing operations.

Identity authorization based on keystroke latencies

Communications of The ACM, 1990

And-Or Parallel Prolog: A Recomputation Based Approach

New Generation Computing, 1993

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Analysis of Or-parallel execution models

ACM Transactions on Programming Languages and Systems, 1993

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Parallel Execution of Prolog Programs: A Survey

ACM Transactions on Programming Languages and Systems, 1995

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Towards a Universal Maths Conversion Library