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On the Computational Complexity of Dynamic Graph Problems
 THEORETICAL COMPUTER SCIENCE
, 1996
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Transformational Design and Implementation Of A New Efficient Solution To The Ready Simulation Problem
 Science of Computer Programming
, 1995
"... A transformational methodology is described for simultaneously designing algorithms and developing programs. The methodology makes use of three transformational tools  dominated convergence, finite differencing, and realtime simulation of a set machine on a RAM. We illustrate the methodology t ..."
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Cited by 42 (2 self)
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A transformational methodology is described for simultaneously designing algorithms and developing programs. The methodology makes use of three transformational tools  dominated convergence, finite differencing, and realtime simulation of a set machine on a RAM. We illustrate the methodology to design a new O(mn + n 2 )time algorithm for deciding when nstate, mtransition processes are ready similar, which is a substantial improvement on the \Theta(mn 6 ) algorithm presented in [6]. The methodology is also used to derive a program whose performance, we believe, is competitive with the most efficient handcrafted implementation of our algorithm. Ready simulation is the finest fully abstract notion of process equivalence in the CCS setting. 1 Introduction Currently there is a wide gap between the goals and practices of research in the theory of algorithm design and the science of programming, which we believe is A preliminary version of this paper appeared in the Conf...
Viewing A Program Transformation System At Work
 Joint 6th International Conference on Programming Language Implementation and Logic Programming (PLILP) and 4th International conference on Algebraic and Logic Programming (ALP), volume 844 of Lecture Notes in Computer Science
, 1994
"... How to decrease labor and improve reliability in the development of efficient implementations of nonnumerical algorithms and labor intensive software is an increasingly important problem as the demand for computer technology shifts from easier applications to more complex algorithmic ones; e.g., opt ..."
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Cited by 26 (2 self)
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How to decrease labor and improve reliability in the development of efficient implementations of nonnumerical algorithms and labor intensive software is an increasingly important problem as the demand for computer technology shifts from easier applications to more complex algorithmic ones; e.g., optimizing compilers for supercomputers, intricate data structures to implement efficient solutions to operations research problems, search and analysis algorithms in genetic engineering, complex software tools for workstations, design automation, etc. It is also a difficult problem that is not solved by current CASE tools and software management disciplines, which are oriented towards data processing and other applications, where the implementation and a prediction of its resource utilization follow more directly from the specification. Recently, Cai and Paige reported experiments suggesting a way to implement nonnumerical algorithms in C at a programming rate (i.e., source lines per second) t...
The Formal Reconstruction and Speedup Of The Linear Time Fragment Of Willard's Relational Calculus Subset
 In Bird and Meertens, editors, Algorithmic Languages and Calculi
, 1997
"... We demonstrate how several programming language concepts and methods can be used economically to obtain an improved solution to a difficult algorithmic problem. The problem is to compile a subset RCS of Relational Calculus defined by Willard (1978) in a novel way so that efficient runtime query per ..."
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Cited by 8 (4 self)
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We demonstrate how several programming language concepts and methods can be used economically to obtain an improved solution to a difficult algorithmic problem. The problem is to compile a subset RCS of Relational Calculus defined by Willard (1978) in a novel way so that efficient runtime query performance is guaranteed. Willard gives an algorithm to compile each query q belonging to RCS so that it executes in O(n log d n+o) steps and O(n) space, where n and o are respectively the input and output set sizes, and d is a parameter associated with the syntax of query q. Willard's time bounds are based on the assumption that hashing unitspace data takes unit time. In this paper we use a settheoretic complexity measure and formal transformational techniques to reconstruct the linear time fragment of RCS in a simplified way. In doing this, we show how complexity can be determined by language abstraction and algebraic reasoning without resorting to low level counting arguments. This ap...
A proposal for a
"... Abstract. The objectives of this research are to improve software productivity, reliability, and performance of complex systems. The approach combines program transformations, sometimes in reflective ways, to turn very high level perspicuous specifications into efficient implementations. These trans ..."
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Cited by 1 (0 self)
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Abstract. The objectives of this research are to improve software productivity, reliability, and performance of complex systems. The approach combines program transformations, sometimes in reflective ways, to turn very high level perspicuous specifications into efficient implementations. These transformations will be implemented in a metatransformational system, which itself will be transformed from an executable specification into efficient code. Experiments will be conducted to assess the research objectives in scaled up applications targetted to systems that perform complex program analysis and translation. The transformations to be used include dominated convergence (for implementing fixed points efficiently), finite differencing (for replacing costly repeated calculations by less expensive incremental counterparts), data structure selection (for simulating associative access on a RAM in real time), and partial evaluation (for eliminating interpretive overhead and simplification). Correctness of these transformations, of userdefined transformations, and of the transformational system itself will be addressed in part. Both the partial evaluator and components of the
Least Reflexive Points of Relations
, 2002
"... Assume a partially ordered set (S, and a relation R on S. We consider various sets of conditions in order to determine whether they ensure the existence of a least reflexive point, that is, a least x such that xRx. This is a generalization of the problem of determining the least fixed point of a ..."
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Assume a partially ordered set (S, and a relation R on S. We consider various sets of conditions in order to determine whether they ensure the existence of a least reflexive point, that is, a least x such that xRx. This is a generalization of the problem of determining the least fixed point of a function and the conditions under which it exists. To motivate the investigation we first present a theorem by Cai and Paige giving conditions under which iterating R from the bottom element necessarily leads to a minimal reflexive point; the proof is by a concise relationalgebraic calculation. Then, we assume a complete lattice and exhibit su#cient conditions, depending on whether R is partial or not, for the existence of a least reflexive point. Further results concern the structure of the set of all reflexive points; among other results we give a su#cient condition that these form a complete lattice, thus generalizing Tarski's classical result to the nondeterministic case.