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74
Graph Drawing by Forcedirected Placement
, 1991
"... this paper, we introduce an algorithm that attempts to produce aestheticallypleasing, twodimensional pictures of graphs by doing simplified simulations of physical systems. We are concerned with drawing undirected graphs according to some generally accepted aesthetic criteria: 1. Distribute the v ..."
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Cited by 431 (0 self)
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this paper, we introduce an algorithm that attempts to produce aestheticallypleasing, twodimensional pictures of graphs by doing simplified simulations of physical systems. We are concerned with drawing undirected graphs according to some generally accepted aesthetic criteria: 1. Distribute the vertices evenly in the frame. 2. Minimize edge crossings. 3. Make edge lengths uniform. 4. Reflect inherent symmetry. 5. Conform to the frame. Our algorithm does not explicitly strive for these goals, but does well at distributing vertices evenly, making edge lengths uniform, and reflecting symmetry. Our goals for the implementation are speed and simplicity. PREVIOUS WORK Our algorithm for drawing undirected graphs is based on the work of Eades which, in turn, evolved from a VLSI technique called forcedirected placement
Performance of Dynamic Load Balancing Algorithms for Unstructured Mesh Calculations
 Concurrency
, 1991
"... If a finite element mesh has a sufficiently regular structure, it is easy to decide in advance how to distribute the mesh among the processors of a distributedmemory parallel processor, but if the mesh is unstructured, the problem becomes much more difficult. The distribution should be made so that ..."
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Cited by 158 (3 self)
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If a finite element mesh has a sufficiently regular structure, it is easy to decide in advance how to distribute the mesh among the processors of a distributedmemory parallel processor, but if the mesh is unstructured, the problem becomes much more difficult. The distribution should be made so that each processor has approximately equal work to do, and such that communication overhead is minimized. If the mesh is solutionadaptive, i.e. the mesh and hence the load balancing problem change discretely during execution of the code, then it is most efficient to decide the optimal mesh distribution in parallel. In this paper three parallel algorithms, Orthogonal Recursive Bisection (ORB), Eigenvector Recursive Bisection (ERB) and a simple parallelization of Simulated Annealing (SA) have been implemented for load balancing a dynamic unstructured triangular mesh on 16 processors of an NCUBE machine. The test problem is a solutionadaptive Laplace solver, with an initial mesh of 280 elements,...
Efficient GraphBased Energy Minimization Methods In Computer Vision
, 1999
"... ms (we show that exact minimization in NPhard in these cases). These algorithms produce a local minimum in interesting large move spaces. Furthermore, one of them nds a solution within a known factor from the optimum. The algorithms are iterative and compute several graph cuts at each iteration. Th ..."
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Cited by 83 (5 self)
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ms (we show that exact minimization in NPhard in these cases). These algorithms produce a local minimum in interesting large move spaces. Furthermore, one of them nds a solution within a known factor from the optimum. The algorithms are iterative and compute several graph cuts at each iteration. The running time at each iteration is eectively linear due to the special graph structure. In practice it takes just a few iterations to converge. Moreover most of the progress happens during the rst iteration. For a certain piecewise constant prior we adapt the algorithms developed for the piecewise smooth prior. One of them nds a solution within a factor of two from the optimum. In addition we develop a third algorithm which nds a local minimum in yet another move space. We demonstrate the eectiveness of our approach on image restoration, stereo, and motion. For the data with ground truth, our methods signicantly outperform standard methods. Biographical Sketch Olga
Face recognition using line edge map
 IEEE Transactions on Pattern Analysis and Machine Intelligence
, 2002
"... AbstractÐThe automatic recognition of human faces presents a significant challenge to the pattern recognition research community. Typically, human faces are very similar in structure with minor differences from person to person. They are actually within one class of ªhuman face.º Furthermore, lighti ..."
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Cited by 65 (3 self)
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AbstractÐThe automatic recognition of human faces presents a significant challenge to the pattern recognition research community. Typically, human faces are very similar in structure with minor differences from person to person. They are actually within one class of ªhuman face.º Furthermore, lighting condition changes, facial expressions, and pose variations further complicate the face recognition task as one of the difficult problems in pattern analysis. This paper proposed a novel concept, ªfaces can be recognized using line edge map.º A compact face feature, Line Edge Map (LEM), is generated for face coding and recognition. A thorough investigation on the proposed concept is conducted which covers all aspects on human face recognition, i.e., face recognition, under 1) controlled/ideal condition and size variation, 2) varying lighting condition, 3) varying facial expression, and 4) varying pose. The system performances are also compared with the eigenface method, one of the best face recognition techniques, and reported experimental results of other methods. A face prefiltering technique is proposed to speed up the searching process. It is a very encouraging finding that the proposed face recognition technique has performed superior to the eigenface method in most of the comparison experiments. This research demonstrates that LEM together with the proposed generic line segment Hausdorff distance measure provide a new way for face coding and recognition. Index TermsÐFace recognition, line edge map, line segment Hausdorff distance, structural information. 1
A Parallel Dynamic Load Balancing Algorithm for 3D Adaptive Unstructured Grids
 AIAA Journal
, 1993
"... Adaptive local grid refinement/coarsening results in unequal distribution of workload among the processors of a parallel system. A novel method for balancing the load in cases of dynamically changing tetrahedral grids is developed. The approach Graduate Research Assistant, Dept. of Electrical and Co ..."
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Cited by 41 (5 self)
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Adaptive local grid refinement/coarsening results in unequal distribution of workload among the processors of a parallel system. A novel method for balancing the load in cases of dynamically changing tetrahedral grids is developed. The approach Graduate Research Assistant, Dept. of Electrical and Computer Engineering y Assistant Professor, Member AIAA z Research Scientist, Member AIAA 1 employs local exchange of cells among processors in order to redistribute the load equally. An important part of the load balancing algorithm is the method employed by a processor to determine which cells within its subdomain are to be exchanged. Two such methods are presented and compared. The strategy for load balancing is based on the DivideandConquer approach which leads to an efficient parallel algorithm. This method is implemented on a distributedmemory MIMD system. 1 Introduction Computational fluid dynamics (CFD) has advanced rapidly over the last two decades and it is recognized as a...
Fast Local Search and Guided Local Search and Their Application to British Telecom's Workforce Scheduling Problem
 Operations Research Letters
, 1995
"... This paper reports a Fast Local Search (FLS) algorithm which helps to improve the efficiency of hill climbing and a Guided Local Search (GLS) Algorithm which is developed to help local search to escape local optima and distribute search effort. To illustrate how these algorithms work, this paper des ..."
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Cited by 40 (20 self)
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This paper reports a Fast Local Search (FLS) algorithm which helps to improve the efficiency of hill climbing and a Guided Local Search (GLS) Algorithm which is developed to help local search to escape local optima and distribute search effort. To illustrate how these algorithms work, this paper describes their application to British Telecom's workforce scheduling problem, which is a hard real life problem. The effectiveness of FLS and GLS are demonstrated by the fact that they both outperform all the methods applied to this problem so far, which include simulated annealing, genetic algorithms and constraint logic programming. I. Introduction Due to their combinatorial explosion nature, many real life constraint optimization problems are hard to solve using complete methods such as branch & bound [17, 14, 21, 23]. One way to contain the combinatorial explosion problem is to sacrifice completeness. Some of the best known methods which use this strategy are local search methods, the ba...
A comparison of annealing techniques for academic course scheduling
 Lecture Notes in Computer Science
, 1998
"... Abstract. In this study we have tackled the NPhard problem of academic class scheduling (or timetabling) at the university level. We have investigated a variety of approaches based on simulated annealing, including meanfield annealing, simulated annealing with three different cooling schedules, an ..."
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Cited by 39 (0 self)
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Abstract. In this study we have tackled the NPhard problem of academic class scheduling (or timetabling) at the university level. We have investigated a variety of approaches based on simulated annealing, including meanfield annealing, simulated annealing with three different cooling schedules, and the use of a rulebased preprocessor to provide a good initial solution for annealing. The best results were obtained using simulated annealing with adaptive cooling and reheating as a function of cost, and a rulebased preprocessor. This approach enabled us to obtain valid schedules for the timetabling problem for a large university, using a complex cost function that includes student preferences. None of the other methods were able to provide a complete valid schedule. 1
A Hardware/Software Partitioner using a dynamically determined Granularity
 In Proceedings of the Design Automation Conference
, 1997
"... Computer aided hardware/software partitioning is one of the key challenges in hardware/software codesign. While previous approaches have used a fixed granularity, i.e. the size of the partitioning objects was fixed, we present a partitioning approach that dynamically determines the partitioning gra ..."
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Cited by 39 (4 self)
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Computer aided hardware/software partitioning is one of the key challenges in hardware/software codesign. While previous approaches have used a fixed granularity, i.e. the size of the partitioning objects was fixed, we present a partitioning approach that dynamically determines the partitioning granularity to adapt optimization steps to application properties and to intermediate optimization results. Experiments with simulated annealing optimization show a faster convergence and far better adaptability to cost function variations than in previous experiments with fixed granularity. 1 Introduction Computer aided hardware/software partitioning is one of the most challenging tasks in codesign. With 100 million transistor systemson achip [1], it will become a key factor for design space exploration and, eventually, be used in automated cosynthesis flow to speed up the design process. Even today, interactive cosynthesis has successfully been used in first industrial projects, where ...
Logic regression
 Journal of Computational and Graphical Statistics
, 2003
"... Logic regression is an adaptive regression methodology that attempts to construct predictors as Boolean combinations of binary covariates. In many regression problems a model is developed that relates the main effects (the predictors or transformations thereof) to the response, while interactions ar ..."
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Cited by 36 (11 self)
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Logic regression is an adaptive regression methodology that attempts to construct predictors as Boolean combinations of binary covariates. In many regression problems a model is developed that relates the main effects (the predictors or transformations thereof) to the response, while interactions are usually kept simple (two to threeway interactions at most). Often, especially when all predictors are binary, the interaction between many predictors may be what causes the differences in response. This issue arises, for example, in the analysis of SNP microarray data or in some data mining problems. In the proposed methodology, given a set of binary predictors we create new predictors such as “X1, X2, X3, and X4 are true, ” or “X5 or X6 but not X7 are true. ” In more speci � c terms: we try to � t regression models of the form g(E[Y]) = b0 + b1L1 + ¢ ¢ ¢ + bnLn, where Lj is any Boolean expression of the predictors. The Lj and bj are estimated simultaneously using a simulated annealing algorithm. This article discusses how to � t logic regression models, how to carry out model selection for these models, and gives some examples.
Problem Independent Distributed Simulated Annealing and Its Applications
 Applications, Applied Simulated Annealing, Lecture Notes in Economics and Mathematical Systems, Springer LNEMS 396
, 1993
"... Simulated annealing has proven to be a good technique for solving hard combinatorial optimization problems. Some attempts at speeding up annealing algorithms have been based on shared memory multiprocessor systems. Also parallelizations for certain problems on distributed memory multiprocessor sy ..."
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Cited by 31 (12 self)
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Simulated annealing has proven to be a good technique for solving hard combinatorial optimization problems. Some attempts at speeding up annealing algorithms have been based on shared memory multiprocessor systems. Also parallelizations for certain problems on distributed memory multiprocessor systems are known.