Array Data Structure Research Articles

Visualising stochastic catchments in geographical networks

Abstract This paper presents an approach to visualising the area of the catchment for a service facility within a network which allows recognition of variability in travel time along the different road segments. By way of illustration fifteen different road conditions are modelled, for the 10 minute travel zone from the Leicester Royal Infirmary. The catchments at each state are then summed, and the resulting composite catchment is visualized as grey scale images, with zones of equal travel time appearing in similar greys. The observed pattern is of a core-periphery catchment, the core having high probabilities of being within a certain travel time, and the periphery having increasingly low probabilities. Four factors which may influence the size and shape of the zones are described. Finally, discussion centres on the shortcomings of both raster and vector data structures for completing the proposed procedure.

Gistt: a geographic information systems teaching tool

Abstract The Geography Department of the University of Auckland has offered a senior level undergraduate course in geographical information systems (GIS) since 1985. The course focuses on providing a good conceptual and practical introduction to GIS as well as teaching spatial analysis within the GIS framework, and is supported by a laboratory programme using both public domain and commercial software. This paper reports a set of programmes developed to introduce students to the fundamental concepts of vector and raster data structures, and to allow them to experiment with procedures for line generalization.

The use of dynamic data structures in finite element applications

AbstractThe derivation of more efficient algorithms for finite element applications is not the primary goal of this article, but rather the efficient implementation of existing algorithms using dynamic data structures. In some cases the algorithms may be far from optimal, but serve to illustrate the advantages of dynamic data structures. In the first section, a tree data structure termed a PATRICIA tree is described and is shown to be suitable for storing data associated with finite element meshes. The manner in which the tree is constructed guarantees to provide rapid data retrieval times, competitive with those associated with static array data structures, whilst providing the added advantages of a dynamic data structure. The second section introduces a list of lists (LOL) data structure which is used to produce an efficient implementation of an example of a bandwidth reduction algorithm. Furthermore, the LOL data structure is also shown to be appropriate for implementing a novel method for extracting the domain boundary, with its orientation, from a given finite element connectivity matrix.

Optimization of array subscript range checks

Compile-time elimination of subscript range checks is performed by some optimizing compilers to reduce the overhead associated with manipulating array data structures. Elimination and propagation, the two methods of subscript range check optimization, are less effective for eliminating global redundancies especially in while-loop structures with nonconstant loop guards. This paper describes a subscript range check optimization procedure that can eliminate more range checks than current methods. Two transformations called inner-loop guard elimination and conservative expression substitution are introduced to enhance propagation of range checks in nested while-loops and to define a partial order on related range checks. Global elimination is improved by considering range checks performed before control reaches a statement and after control leaves a statement. A unique feature of this method is the simplification of the available range-check analysis system for global elimination.

Artificial intelligence approach to planning the robotic assembly of large tetrahedral truss structures

This article presents an assembly sequence planner for tetrahedral truss structures. To overcome the difficulties due to the large number of parts, the planner exploits the simplicity and uniformity of the shapes of the parts and the regularity of their interconnection. The planning automation is based on the computational formalism known as production system. The global database consists of an hexagonal grid representation of the truss structure. This representation captures the regularity of tetrahedral truss structures and their multiple hierarchies. It maps into quadratic grids and can be implemented in a computer by using a two dimensional array data structure. By maintaining the multiple hierarchies explicitly in the model, the choice of a particular hierarchy is only made when needed, thus allowing a more informed decision. Furthermore, testing the preconditions of the production rules is simple because the patterned way in which the struts are interconnected is incorporated into the topology of the hexagonal grid. A directed graph representation of assembly sequences allows the use of both graph search and backtracking control strategies.

Processor-efficient implementation of a maximum flow algorithm

We describe two parallel implementations of the Maximum Distance Discharge algorithm for the maximum flow problems. Both implementations achieve near-optimal speedup for up to a linear number of processors. One of the implementations uses a new dynamic array data structure.

An algorithm for string matching with a sequence of don't cares

We present an algorithm to search for a pattern containing a sequence of don't care symbols in a preprocessed text. This problem models proximity searching in text searching systems and special searching problems in biological sequences. The main result is that the suffix array data structure of Manber and Myers can be used to reduce this problem to the two-dimensional orthogonal range queries problem. Using known results for the latter problem we obtain a data structure that uses O( n( k + m)) space, where n is the size of the text, k is an upper bound on the number of don't care symbols and m is an upper bound on the number of characters of the pattern appearing before the don't care symbols. The number of occurrences of the pattern can be found in O(log n) time, and a list of all occurrences can be found in time O( n /4 + R), where R is the number of occurrences.

Systolic arrays for group explicit methods for solving first order hyperbolic equations

In this paper, systolic techniques for the simulation of the Group Explicitmethod for parabolic equations by systolic array data structures using the Soft Systolic algorithm paradigm have been extended to include hyperbolic equations of first order. In particular, the Group Explicit Complete (GEC) strategy can be used as generic array construction for other simple schemes and for comput ations on large intervals. The easy form of the finite difference approximation to the hyperbolic equation res ults in a simpler and hence faster and more area efficient basic cell.

Formal specification of data abstraction in FORTRAN 77: abstract arrays

The emphasis of data organisation on the specification, design and implementation of large systems raises the question whether data abstraction may be applied to programming languages designed before the widespread use of such techniques. The data abstraction facilities available in FORTRAN 77 are considered and it is shown that encapsulation is possible for simple data structures. An abstract array data structure is specified and further refined to allow the definition of iterators. An example of this structure is implemented in FORTRAN 77. The introduction of a series of abstractions is thus made possible which facilitates structured development and efficient maintenance. >

A logical basis for nested array data structures

A logical description of array data structures is presented as an extension of a theory of equality over lists. It provides axioms and theorems that describe the data objects of the Nested Interactive Array Language, Nial. A model for the theory is presented, and the application of the theory to the development of a logic programming extension to Nial is described.

Local Transformations via Cube Operations

Wislan is a language for describing computer hardware at the gate and functional levels of abstraction. After converting a WISLAN description to a gate table data structure, users interactively apply local transformations to that network to transform the gate network to a technology, meet technology limits, and optimize the network. A number of extensions to WISLAN and new, less-local transforms are reported. The transforms are made efficient via operations on array representations of switching functions. Conversion between gate table and array data structures is also efficient.

Design and Performance Evaluation of EXMAN: An EXtended MANchester Data Flow Computer

Data flow computers are high-speed machines in which an instruction is executed as soon as all its operands are available. This paper describes the EXtended MANchester (EXMAN) data flow computer which incorporates three major extensions to the basic Manchester machine. As extensions we provide a multiple matching units scheme, an efficient, implementation of array data structure, and a facility to concurrently execute reentrant routines. A simulator for the EXMAN computer has been coded in the discrete event simulation language, SIMULA 67, on the DEC 1090 system. Performance analysis studies have been conducted on the simulated EXMAN computer to study the effectiveness of the proposed extensions. The performance experiments have been carried out using three sample problems: matrix multiplication, Bresenham's line drawing algorithm, and the polygon scan-conversion algorithm.

A data-flow multiprocessor architecture for the transform coding of regularly decomposed images

An architecture for the parallel implementation of an orthogonal transform of images is presented. Images are preprocessed by the “regular decomposition” procedure and converted into a quad-tree representation. The orthogonal transformation is performed progressivelly by adjusting to the various hierarchies of the quad-tree nodes. The architecture of the proposed machine is based on the data-driven model of computation in which an operation is executed when its operands are available. The specific requirements of the image processing algorithms have been taken into account, principally the efficient handling of array data-structures. The tagged-token method supports recursive operations and helps to better exploit the inherent parallelism of the transformation algorithms.

On-Line Information and Control Systems for Large Power Pools-Data Structures and Processor Structures

Real time computer systems, needed by a large scale interconnected power system, are expected to synthesize the following important functions; a) data logging, load predictions, direct control, optimal and adaptive controls; (b) data bank, management functions and performance analyses; (c) energy information, planning and other background processing.This paper deals with an optimal control strategy for scheduling of thermal plants using the Jacobian matrix of Newton’s load flow equations repeatedly leading to faster solution.A static data structure of a two dimensional array has been developed to store the triangulated admittance matrix (only non zero terms are stored) and a modified algorithm has been employed to solve the resultant systems of linear equations. This algorithm retains sparsity and makes use of the symmetric structure of admittance matrix to reduce operations. The static array data structure needs lesser number of locations for storage than the commonly used linked list structure. Further, its constancy during iterations - leading to permanancy of its storage locations - results in considerable reduction in computer time.It is possible to synthesize this strątegy through the use of distributed processors.

Even Simple Programs Are Hard To Analyze

A simple programming language which corresponds in computational power to the class of generalized sequential machines with final states is defined. It is shown that a variety of questions of practical programming interest about the language are of nondeterministic linear space complexity. Extensions to the language are defined (adding arithmetic and array data structures) and their complexity properties are explored. It is concluded that questions about halting, equivalence, optimization, and so on are intractable even for very simple programming languages.

On storing ragged arrays by hashing

The inevitably poor utilization of storage by computed-access realizations of extendible rectangular arrays can be circumvented by storing such arrays by hashing. This paper studies the extent to which the same switch in storage strategy avoids the even worse utilization of storage by computed-access realizations of extendible ragged (i.e., nonrectangular) arrays. Unfortunately, the dramatic successes of the rectangular case do not carry over: any hashing scheme for extendible ragged arrays with storage demands very much smaller than those of computed-access realizations must suffer expected access time that is close to worst possible. On the other hand, one can obtain moderate savings in storage demands by hashing ragged arrays, together with sufferable access time. This last result issues from a general technique for trading increased access time for savings in storage. Even more striking savings are attainable if one restricts attention tofully-justified ragged arrays, whose raggedness is more regular than that of general ragged arrays. However, the overall impact of our results is that extendible ragged arrays do not succumb to the storage strategies that work efficiently on their rectangular counterparts.