Johns Hopkins University Department of Computer ScienceOverview
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Most widely held works by
Johns Hopkins University
Sorting on a parallel pointer machine with applications to set expression evaluation
by Michael T Goodrich
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Book
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2 editions published between 1989 and 1991 in English and held by 2 WorldCat member libraries worldwide Abstract: "We present optimal algorithms for sorting on parallel CREW and EREW versions of the pointer machine model. Intuitively, one can view our methods as being based on the use of linked lists rather than arrays (the usual parallel data structure). We also show how to exploit the 'locality' of our approach to solve the set expression evaluation problem, a problem with applications to database querying and logic programming, in 0(log n) time using 0(n) processors. Interestingly, this is an asymptotic improvement over what seems possible using previous techniques."
The bisector of a point and a plane parametric curve
by Rida A. M. T Farouki
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Book
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1 edition published in 1991 in English and held by 2 WorldCat member libraries worldwide Abstract: "The bisector of a fixed point p and a smooth plane curve C  i.e., the locus traced by a point that remains equidistant with respect to p and C  is investigated in the case that C admits a regular polynomial or rational parameterization. It is shown that the bisector may be regarded as (a subset of) a 'variabledistance' offset curve to C which has the attractive property, unlike fixeddistance offsets, of being generically a rational curve. This 'untrimmed bisector' usually exhibits irregular points and selfintersections similar in nature to those seen on fixeddistance offsets. A trimming procedure, which identifies the parametric subsegments of this curve that constitute the true bisector, is described in detail. The bisector of the point p and any finite segment of the curve C is also discussed."
Outputsensitive hidden surface elimination for rectangles
by Mikhail J Atallah
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Book
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1 edition published in 1988 in English and held by 2 WorldCat member libraries worldwide Abstract: "We present an algorithm for the wellknown hiddensurface elimination problem for rectangles, which is also known as the window rendering problem. The time complexity of our algorithm is sensitive to the size of the output. Specifically, it runs in time that is O (n [superscript 1.5] + k), where k is the size of the output (which can be as large as [theta] (n [squared])). For values of k in the range between n [superscript 1.5] / log n and n [squared], our algorithm is asymptotically faster than previous ones."
A comparison of three hidden line removal algorithms
by Larry B Hostetler
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Book
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1 edition published in 1989 in English and held by 2 WorldCat member libraries worldwide Abstract: "Three algorithms for hidden line removal by Devai [4], Goodrich [6], and Schmitt [8], are compared on the basis of their execution times over a test set of schemes to be displayed."
Computing the center of area of a simple polygon
by Matthew Díaz
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Book
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1 edition published in 1989 in English and held by 2 WorldCat member libraries worldwide Abstract: "The center of area of a polygon P is the unique point [formula] that maximizes the minimum area overlap between P and any halfplane that includes [formula]. A "numerical" algorithm was presented in [DO88] for finding the coordinates of [formula] for a convex polygon of n vertices. In this paper we present an extension of this algorithm for nonconvex polygons. All of these algorithms are numerical in the sense that we have been careful to express the algorithm complexities as a function of G, the number of bits used to represent the coordinates of polygon vertices, and K, thenumber of desired bits of precision in the output coordinates of [formula]
Outputsensitive methods for rectilinear hidden surface removal
by Michael T Goodrich
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Book
)
1 edition published in 1990 in English and held by 2 WorldCat member libraries worldwide Abstract: "We present an algorithm for the hiddensurface elimination problem for rectangles, which is also known as window rendering. The time complexity of our algorithm is dependent on both the number of input rectangles, n, and on the size of the output, k. Our algorithm obtains a tradeoff between these two components, in that its running time is [formula], where 1 [less than or equal to] r [less than or equal to] log n is a tunable parameter. By using this method while adjusting the parameter r 'on the fly' one can achieve a running time that is O(n log n+k(log n/log(1+k/n))). Note that when k is [Theta](n), this achieves an O(n log n) running time, and when k is [formula] for any positive constant [epsilon], then this achieves an O(k) running time, both of which are optimal."
Computing the intersection of a plane and a natural quadric
by John K Johnstone
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Book
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1 edition published in 1991 in English and held by 1 WorldCat member library worldwide Abstract: "A method of computing the intersection of a plane and a natural quadric surface is presented. This problem is basic in geometric areas such as solid modeling and descriptive geometry. Our method, arising out of recent work on lower degree intersections of quadrics, computes the directions of the axes of the intersection, and then computes their lengths using the Dandelin sphere. The method also gives all parallel plane sections of the natural quadric, with no added computation."
Merging free trees in parallel for efficient Voronoi diagram construction
by Richard Cole
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Book
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1 edition published in 1989 in English and held by 1 WorldCat member library worldwide Abstract: "This paper describes a new approach for constructing the Voronoi diagram of n points in the plane in parallel. Our approach is based on a divideandconquer procedure where we implement the 'marry' step by merging forests of free trees (to build the 'contour' between the subprogram solutions) in O(log log n) time. This merging procedure is based an a [square root]ndivideandconquer merge technique reminiscent of the listmerging approach of Valiant. Our method also involves an optimal parallel method for computing the proximity envelope of a point set with respect to a given line
Algorithms for computing the center of area of a convex polygon
by Matthew Díaz
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Book
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1 edition published in 1988 in English and held by 1 WorldCat member library worldwide Abstract: "Given a convex polygon P, associate with each point p [is a member of] P the minimum area of the polygon to the left of any chord through p. The maximum over all points in P is known as 'Winternitz's Measure of Symmetry' and the point p[superscript *] that achieves this maximum we call the center of area. We will show that p[superscript *] is unique and derive geometric properties of minimumarea chords. These properties lead to two algorithms for computing the center of area of a convex polygon with n vertices. The first is a combinatorial algorithm that runs in time O(n[superscript 6]log[superscript 2]n). The second in a numerical algorithm that computes the coordinates to K bits of precision in time O(nK). We conclude with a discussion of our implementation of the second algorithm, extensions to higher dimensions and other generalizations."
Inplace techniques for parallel convex hull algorithms
by Mujtaba R Ghouse
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Book
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1 edition published in 1991 in English and held by 1 WorldCat member library worldwide
Dupin cyclides as blending surfaces for cones
by John K Johnstone
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Book
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1 edition published in 1992 in English and held by 1 WorldCat member library worldwide
A numerical method for rendering sphere reflections
by E. S Panduranga
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Book
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1 edition published in 1989 in English and held by 1 WorldCat member library worldwide This algorithm has exhibited many attractive properties, e.g., low computation cost, objectspaceoriented therefore resolution and device independence, etc. Moreover, it provides a guideline for future research interest, that it, it is quite likely to generalize this method to render reflections in a family of curved surfaces."
Virtually defectfree code as a direct result of a welldefined comprehensive testing method
by Phillis A Schneck
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Book
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1 edition published in 1991 in English and held by 1 WorldCat member library worldwide Abstract: "The upgrading and refinement of the test plans and processes currently used in the construction of large software systems makes the production of virtually defectfree code has [sic] become a reality. The primary purpose of this paper is to document and build the basis for a comprehensive approach to testing that has proven successful in developing and delivering defectfree code."
Constructing arrangements optimally in parallel
by Michael T Goodrich
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Book
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1 edition published in 1990 in English and held by 1 WorldCat member library worldwide
A polygonal approach to hiddenline and hiddensurface elimination
by Michael T Goodrich
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Book
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1 edition published in 1988 in English and held by 1 WorldCat member library worldwide Abstract: "We present algorithms for the wellknown hiddenline and hiddensurface elimination problems. Our algorithms are optimal in the worst case, and are also able to take advantage of problem instances that are 'simpler' than in the worst case. Specifically, our algorithms run in O(n log n + k + t) time, where n is the number of edges, and k (resp. t) is the number of intersecting pairs of line segments (resp. polygons) in the projection plane [pi]. Our algorithms are based on a polygonbased strategy, rather than an edgebased strategy, and are quite simple."
On the power of probabilistic polynomial time : (extended abstract)
by Richard Beigel
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Book
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1 edition published in 1989 in English and held by 1 WorldCat member library worldwide Abstract: "We show that probabilistic polynomial time is closed under polynomialtime parity reductions. Therefore every set polynomialtime truthtable reducible to SAT (every set in the [formula] level of the polynomial hierarchy) is accepted by a probabilistic polynomialtime Turing machine. Equivalently, [formula]."
Hyperbolic paraboloids and the correspondence between two lines
by John K Johnstone
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Book
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1 edition published in 1990 in English and held by 1 WorldCat member library worldwide In order to work with this alternate representation, computational results are provided. Given the implicit or parametric representation of an appropriate hyperbolic paraboloid, we show how to compute the two parameterized lines that represent it. Given two parameterized skew lines, we show how to compute the implicit and parametric representation of the hyperbolic paraboloid that they represent. During the development of these results, the relationship between the hyperbolic paraboloid and the bilinear parameterization is clarified; and the plane is considered as a degenerate form of the hyperbolic paraboloid."
A comparison of learning methods that use geometric primitives
by Steven L Salzberg
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Book
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1 edition published in 1991 in English and held by 1 WorldCat member library worldwide Abstract: "This paper compares four inductive learning techniques that employ geometric primitives for their generalization processes. A geometric primitive is any simple geometric object, such as a line or a circle, that may be used to build concept descriptions. Each method learns from examples, where an example consists of a vector of realvalued features plus a label. The learning problem is to produce a model that correctly assigns labels to new examples in the feature space. Our experiments show that, although the methods have various conceptual features that are in each case desirable, experimental performance does not clearly favor any of them
Efficient parallel term matching
by Art Delcher
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Book
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1 edition published in 1988 in English and held by 1 WorldCat member library worldwide Abstract: "In this paper we present several O (N/log [squared] N)processors, O (log [squared] N)time EREW PRAM parallel algorithms for term matching problems. Term matching is the special case of unification in which one of the terms is restricted to contain no variables. It has wide applicability to logic programming, term rewriting systems and symbolic pattern matching used in Artificial Intelligence. Antiunification is the dual problem of unification in which one computes the most specific generalization of two terms. It has application to inductive inference and theorem proving. The algorithms presented are the first to have a processor x time product of the same order as that of the sequential algorithm, thus ensuring optimal speedups using any number of processors up to O(N/log [squared] N)."
Intersecting line segments in parallel with an outputsensitive number of processors
by Michael T Goodrich
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Book
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1 edition published in 1988 in English and held by 1 WorldCat member library worldwide The algorithm does not receive the value of k as input, it determines it online. We also show how to solve an important special case of the segment arrangement problem, namely, when each input segments is parallel to one of the coordinate axes (i.e., isooriented). Our algorithm for this problem runs in O(log n) time using an optimal O(n+k/log n) processors in the CREW PRAM model." more
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Associated Subjects
Algorithms Computational complexity Computer graphics Cone Curves Data structures (Computer science) Geometry Geometry, Plane GeometryData processing Logic programming Machine learning Parabola Parallel processing (Electronic computers) Polygons Polynomials Rectangles Software engineering Sorting (Electronic computers) Sphere Surfaces, Algebraic Voronoi polygons

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