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167
An Empirical Study of Algorithms for Point Feature Label Placement
, 1994
"... A major factor affecting the clarity of graphical displays that include text labels is the degree to which labels obscure display features (including other labels) as a result of spatial overlap. Pointfeature label placement (PFLP) is the problem of placing text labels adjacent to point features on ..."
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Cited by 133 (8 self)
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A major factor affecting the clarity of graphical displays that include text labels is the degree to which labels obscure display features (including other labels) as a result of spatial overlap. Pointfeature label placement (PFLP) is the problem of placing text labels adjacent to point features on a map or diagram so as to maximize legibility. This problem occurs frequently in the production of many types of informational graphics, though it arises most often in automated cartography. In this paper we present a comprehensive treatment of the PFLP problem, viewed as a type of combinatorial optimization problem. Complexity analysis reveals that the basic PFLP problem and most interesting variants of it are NPhard. These negative results help inform a survey of previously reported algorithms for PFLP; not surprisingly, all such algorithms either have exponential time complexity or are incomplete. To solve the PFLP problem in practice, then, we must rely on good heuristic methods. We pr...
A Heuristic Method for the Set Covering Problem
 OPERATIONS RESEARCH
, 1995
"... We present a Lagrangianbased heuristic for the wellknown Set Covering Problem (SCP). The algorithm was initially designed for solving very large scale SCP instances, involving up to 5,000 rows and 1,000,000 columns, arising from crew scheduling in the Italian Railway Company, Ferrovie dello St ..."
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Cited by 62 (8 self)
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We present a Lagrangianbased heuristic for the wellknown Set Covering Problem (SCP). The algorithm was initially designed for solving very large scale SCP instances, involving up to 5,000 rows and 1,000,000 columns, arising from crew scheduling in the Italian Railway Company, Ferrovie dello Stato SpA. In 1994 Ferrovie dello Stato SpA, jointly with the Italian Operational Research Society, organized a competition, called FASTER, intended to promote the development of algorithms capable of producing good solutions for these instances, since the classical approaches meet with considerable difficulties in tackling them. The main characteristics of the algorithm we propose are (1) a dynamic pricing scheme for the variables, akin to that used for solving largescale LP's, to be coupled with subgradient optimization and greedy algorithms, and (2) the systematic use of column fixing to obtain improved solutions. Moreover, we propose a number of improvements on the standard way o...
Convex Nondifferentiable Optimization: A Survey Focussed On The Analytic Center Cutting Plane Method.
, 1999
"... We present a survey of nondifferentiable optimization problems and methods with special focus on the analytic center cutting plane method. We propose a selfcontained convergence analysis, that uses the formalism of the theory of selfconcordant functions, but for the main results, we give direct pr ..."
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Cited by 51 (2 self)
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We present a survey of nondifferentiable optimization problems and methods with special focus on the analytic center cutting plane method. We propose a selfcontained convergence analysis, that uses the formalism of the theory of selfconcordant functions, but for the main results, we give direct proofs based on the properties of the logarithmic function. We also provide an in depth analysis of two extensions that are very relevant to practical problems: the case of multiple cuts and the case of deep cuts. We further examine extensions to problems including feasible sets partially described by an explicit barrier function, and to the case of nonlinear cuts. Finally, we review several implementation issues and discuss some applications.
Analyzing and Exploiting the Structure of the Constraints in the ILP Approach to the Scheduling Problem
 IEEE Transactions on VLSI Systems
, 1994
"... In integer linear programming (ILP), formulating a "good" model is of crucial importance to solving that model [1]. In this paper, we begin with a mathematical analysis of the structure of the assignment, timing, and resource constraints in highlevel synthesis, and then evaluate the structure of th ..."
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Cited by 47 (8 self)
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In integer linear programming (ILP), formulating a "good" model is of crucial importance to solving that model [1]. In this paper, we begin with a mathematical analysis of the structure of the assignment, timing, and resource constraints in highlevel synthesis, and then evaluate the structure of the scheduling polytope described by these constraints. We then show how the structure of the constraints can be exploited to develop a wellstructured ILP formulation, which can serve as a solid theoretical foundation for future improvement. As a start in that direction, we also present two methods to further tighten the formulation. The contribution of this paper is twofold: (1) it provides the first indepth formal analysis of the structure of the constraints, and it shows how to exploit that structure in a welldesigned ILP formulation, and (2) it shows how to further improve a wellstructured formulation by adding new valid inequalities. I. Introduction The scheduling problem in highle...
On Ascending Vickrey Auctions for Heterogeneous Objects
, 2005
"... We construct an ascending auction for heterogeneous objects by applying a primaldual algorithm to a linear program that represents the efficientallocation problem for this setting. The auction assigns personalized prices to bundles, and asks bidders to report their preferred bundles in each round. ..."
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Cited by 44 (4 self)
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We construct an ascending auction for heterogeneous objects by applying a primaldual algorithm to a linear program that represents the efficientallocation problem for this setting. The auction assigns personalized prices to bundles, and asks bidders to report their preferred bundles in each round. A bidder’s prices are increased when he belongs to a “minimally undersupplied ” set of bidders. This concept generalizes the notion of “overdemanded” sets of objects introduced by Demange et al. (1986) for the onetoone assignment problem. Under a submodularity condition, the auction implements the Vickrey–Clarke–Groves outcome; we show that this type of condition is somewhat necessary to do so. When classifying the ascendingauction literature in terms of their underlying algorithms, our auction fills a gap in that literature. We relate our results to various ascending auctions in the literature.
The Exponentiated Subgradient Algorithm for Heuristic Boolean Programming
 IN PROC. IJCAI01
, 2001
"... Boolean linear programs (BLPs) are ubiquitous in AI. Satisfiability testing, planning with resource constraints, and winner determination in combinatorial auctions are all examples of this type of problem. Although increasingly wellinformed by work in OR, current AI research has tended to focu ..."
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Cited by 44 (2 self)
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Boolean linear programs (BLPs) are ubiquitous in AI. Satisfiability testing, planning with resource constraints, and winner determination in combinatorial auctions are all examples of this type of problem. Although increasingly wellinformed by work in OR, current AI research has tended to focus on specialized algorithms for each type of BLP task and has only loosely patterned new algorithms on effective methods from other tasks. In this paper we introduce a single generalpurpose local search procedure that can be simultaneously applied to the entire range of BLP problems, without modification. Although one might suspect that a generalpurpose algorithm might not perform as well as specialized algorithms, we find that this is not the case here. Our experiments show that our generic algorithm simultaneously achieves performance comparable with the state of the art in satisfiability search and winner determination in combinatorial auctions two very different BLP problems. Our algorithm is simple, and combines an old idea from OR with recent ideas from AI.
A Minimal Algorithm for the MultipleChoice Knapsack Problem.
 European Journal of Operational Research
, 1994
"... The MultipleChoice Knapsack Problem is defined as a 01 Knapsack Problem with the addition of disjoined multiplechoice constraints. As for other knapsack problems most of the computational effort in the solution of these problems is used for sorting and reduction. But although O(n) algorithms whic ..."
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Cited by 42 (4 self)
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The MultipleChoice Knapsack Problem is defined as a 01 Knapsack Problem with the addition of disjoined multiplechoice constraints. As for other knapsack problems most of the computational effort in the solution of these problems is used for sorting and reduction. But although O(n) algorithms which solves the linear MultipleChoice Knapsack Problem without sorting have been known for more than a decade, such techniques have not been used in enumerative algorithms.
A video compression scheme with optimal bit allocation between displacement vector field and displaced frame difference
 in Proc. IEEE International Conference on Image Processing
, 1997
"... In objectbased video, the encoding of the video data is decoupled into the encoding of shape, motion and texture information, which enables certain functionalities like contentbased interactivity and scalability. However, the problem of how to jointly encode these separate signals to reach the bes ..."
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Cited by 33 (12 self)
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In objectbased video, the encoding of the video data is decoupled into the encoding of shape, motion and texture information, which enables certain functionalities like contentbased interactivity and scalability. However, the problem of how to jointly encode these separate signals to reach the best coding efficiency has never been solved thoroughly. In this paper, we present an operational ratedistortion optimal bit allocation scheme that provides a solution to this problem. Our approach is based on the Lagrangian relaxation and dynamic programming. Experimental results indicate that the proposed optimal encoding approach has considerable gains over an adhoc method without optimization. Furthermore the proposed algorithm is much more efficient than exhaustive search. 1.
Dynamic Rate Shaping of Compressed Digital Video
 In Proc. of 2 nd IEEE Intl. Conf. on Image Processing
, 1995
"... We discuss new theoretical and experimental results on the Dynamic Rate Shaping (DRS) approach for transcoding compressed video bitstreams (MPEG1, MPEG2, MPEG4, H.261 as well as JPEG). A set of low complexity algorithms for both constrained and unconstrained DRS are presented. We present the firs ..."
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Cited by 30 (4 self)
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We discuss new theoretical and experimental results on the Dynamic Rate Shaping (DRS) approach for transcoding compressed video bitstreams (MPEG1, MPEG2, MPEG4, H.261 as well as JPEG). A set of low complexity algorithms for both constrained and unconstrained DRS are presented. We present the first extensive experimental study on the various DRS algorithms (causally optimal, memoryless, and ratebased) both in their constrained and generalized forms. The study proves the computational viability of the DRS approach to transcoding and identifies a range of rate shaping ratios for which it is better than requantization, both complexitywise as well as in performance. We then substantiate the almostoptimal experimental performance of the memoryless algorithm by analyzing the behavior of the DRS problem assuming a first order Autoregressive source. By deriving the statistical and ratedistortion characteristics of different components of the interframe rate shaping problem, we offer an explanation as to why the set of optimal breakpoint values for any frame is somewhat invariant to the accumulated motion compensated shaping error from past frames. This result is significant as it opens up the way to construct much simpler memoryless algorithms that give minimal penalty in achieved quality, not just for this, but possibly other types of algorithms. Of equal, if not more, importance is the very first use of matrix perturbation theory for tracking the spectral behavior of the autocorrelation matrix of the source signal and the motion residual it yields. 1 1