Results 1  10
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31
Problems in Computational Geometry
 Packing and Covering
, 1974
"...  reproduced, stored In a retrieval system, or transmlt'ted, In any form or by any means, electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author. ..."
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Cited by 480 (2 self)
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 reproduced, stored In a retrieval system, or transmlt'ted, In any form or by any means, electronic, mechanical, photocopying, or otherwise, without the prior written permission of the author.
Cones Of Matrices And Successive Convex Relaxations Of Nonconvex Sets
, 2000
"... . Let F be a compact subset of the ndimensional Euclidean space R n represented by (finitely or infinitely many) quadratic inequalities. We propose two methods, one based on successive semidefinite programming (SDP) relaxations and the other on successive linear programming (LP) relaxations. Each ..."
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Cited by 50 (21 self)
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. Let F be a compact subset of the ndimensional Euclidean space R n represented by (finitely or infinitely many) quadratic inequalities. We propose two methods, one based on successive semidefinite programming (SDP) relaxations and the other on successive linear programming (LP) relaxations. Each of our methods generates a sequence of compact convex subsets C k (k = 1, 2, . . . ) of R n such that (a) the convex hull of F # C k+1 # C k (monotonicity), (b) # # k=1 C k = the convex hull of F (asymptotic convergence). Our methods are extensions of the corresponding LovaszSchrijver liftandproject procedures with the use of SDP or LP relaxation applied to general quadratic optimization problems (QOPs) with infinitely many quadratic inequality constraints. Utilizing descriptions of sets based on cones of matrices and their duals, we establish the exact equivalence of the SDP relaxation and the semiinfinite convex QOP relaxation proposed originally by Fujie and Kojima. Using th...
Movable Separability of Sets
 Computational Geometry
, 1985
"... Spurred by developments in spatial planning in robotics, computer graphics, and VLSI layout, considerable attention has been devoted recently to the problem of moving sets of objects, such as line segments and polygons in the plane to polyhedra in three dimensions, without allowing collisions betwee ..."
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Cited by 39 (4 self)
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Spurred by developments in spatial planning in robotics, computer graphics, and VLSI layout, considerable attention has been devoted recently to the problem of moving sets of objects, such as line segments and polygons in the plane to polyhedra in three dimensions, without allowing collisions between the objects. One class of such problems considers the separability of sets of objects under different kinds of motions and various definitions of separation. This paper surveys this new area of research in a tutorial fashion, present new results, and provides a list of open problems and suggestions for further research. Key Words and Phrases: sofa problem, polygons, polyhedra, movable separability, visibility hulls, hidden lines, hidden surfaces, algorithms, complexity, computational geometry, spatial planning, collision avoidance, robotics, artificial intelligence. CR Categories: 3.36, 3.63, 5.25. 5.32. 5.5 * Research supported by NSERC Grant no. A9293 and FCAR Grant no.EQ1678.  2  ...
Exposing Constraints
, 1992
"... The development of algorithms and software for the solution of largescale optimization problems has been the main motivation behind the research on the identification properties of optimization algorithms. The aim of an identification result for a linearly constrained problem is to show that if the ..."
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Cited by 24 (1 self)
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The development of algorithms and software for the solution of largescale optimization problems has been the main motivation behind the research on the identification properties of optimization algorithms. The aim of an identification result for a linearly constrained problem is to show that if the sequence generated by an optimization algorithm converges to a stationary point, then there is a nontrivial face F of the feasible set such that after a finite number of iterations, the iterates enter and remain in the face F . This paper develops the identification properties of linearly constrained optimization algorithms without any nondegeneracy or linear independence assumptions. The main result shows that the projected gradient converges to zero if and only if the iterates enter and remain in the face exposed by the negative gradient. This result generalizes results of Burke and Moré obtained for nondegenerate cases.
Complementarity Constraint Qualifications and Simplified BStationarity Conditions for Mathematical Programs with Equilibrium Constraints
, 1998
"... With the aid of some novel complementarity constraint qualifications, we derive some simplied primaldual characterizations of a Bstationary point for a mathematical program with complementarity constraints (MPEC). The approach is based on a locally equivalent piecewise formulation of such a prog ..."
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Cited by 21 (6 self)
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With the aid of some novel complementarity constraint qualifications, we derive some simplied primaldual characterizations of a Bstationary point for a mathematical program with complementarity constraints (MPEC). The approach is based on a locally equivalent piecewise formulation of such a program near a feasible point. The simplied results, which rely heavily on a careful dissection and improved understanding of the tangent cone of the feasible region of the program, bypass the combinatorial characterization that is intrinsic to Bstationarity.
Constrained Discounted Dynamic Programming
 MATH. OF OPERATIONS RESEARCH
, 1996
"... This paper deals with constrained optimization of Markov Decision Processes with a countable state space, compact action sets, continuous transition probabilities, and upper semicontinuous reward functions. The objective is to maximize the expected total discounted reward for one reward function, u ..."
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Cited by 18 (8 self)
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This paper deals with constrained optimization of Markov Decision Processes with a countable state space, compact action sets, continuous transition probabilities, and upper semicontinuous reward functions. The objective is to maximize the expected total discounted reward for one reward function, under several inequality constraints on similar criteria with other reward functions. Sippose a
LowDimensional Lattices VII: Coordination Sequences
 Proc. Royal Soc. A453
, 1996
"... The coordination sequence fS(n)g of a lattice or net gives the number of nodes that are n bonds away from a given node. S(1) is the familiar coordination number. Extending work of O'Keeffe and others, we give explicit formulae for the coordination sequences of the root lattices A d , D d , E 6 ..."
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Cited by 8 (0 self)
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The coordination sequence fS(n)g of a lattice or net gives the number of nodes that are n bonds away from a given node. S(1) is the familiar coordination number. Extending work of O'Keeffe and others, we give explicit formulae for the coordination sequences of the root lattices A d , D d , E 6 , E 7 , E 8 and their duals. Proofs are given for many of the formulae, and for the fact that in every case S(n) is a polynomial in n, although some of the individual formulae are conjectural. In the majority of cases the set of nodes that are at most n bonds away from a given node form a polytopal cluster whose shape is the same as that of the contact polytope for the lattice. It is also shown that among all the Barlow packings in three dimensions the hexagonal close packing has the greatest coordination sequence, and the facecentered cubic lattice the smallest, as conjectured by O'Keeffe. 1. Introduction The coordination sequence of an infinite vertextransitive graph G is the sequence fS...
Cost approximation: A unified framework of descent algorithms for nonlinear programs
 SIAM Journal on Optimization
, 1994
"... . The paper describes and analyzes the cost approximation algorithm. This class of iterative descent algorithms for nonlinear programs and variational inequalities places a large number of algorithms within a common framework and provides a means for analyzing relationships among seemingly unrelated ..."
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Cited by 7 (4 self)
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. The paper describes and analyzes the cost approximation algorithm. This class of iterative descent algorithms for nonlinear programs and variational inequalities places a large number of algorithms within a common framework and provides a means for analyzing relationships among seemingly unrelated methods. A common property of the methods included in the framework is that their subproblems may be characterized by monotone mappings, which replace an additive part of the original cost mapping in an iterative manner; alternately, a step is taken in the direction obtained in order to reduce the value of a merit function for the original problem. The generality of the framework is illustrated through examples, and the convergence characteristics of the algorithm are analyzed for applications to nondifferentiable optimization. The convergence results are applied to some example methods, demonstrating the strength of the analysis compared to existing results. Key Words. Nondifferentiable o...
Conewise linear systems: nonZenoness and observability
 SIAM J. Control Optim
"... Abstract. Conewise linear systems are dynamical systems in which the state space is partitioned into a finite number of nonoverlapping polyhedral cones on each of which the dynamics of the system is described by a linear differential equation. This class of dynamical systems represents a large numbe ..."
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Cited by 7 (1 self)
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Abstract. Conewise linear systems are dynamical systems in which the state space is partitioned into a finite number of nonoverlapping polyhedral cones on each of which the dynamics of the system is described by a linear differential equation. This class of dynamical systems represents a large number of piecewise linear systems, most notably, linear complementarity systems with the Pproperty and their generalizations to affine variational systems, which have many applications in engineering systems and dynamic optimization. The challenges of dealing with this type of hybrid system are due to two major characteristics: mode switchings are triggered by state evolution, and states are constrained in each mode. In this paper, we first establish the absence of Zeno states in such a system. Based on this fundamental result, we then investigate and relate several state observability notions: shorttime and Ttime (or finitetime) local/global observability. For the shorttime observability notions, constructive, finitely verifiable algebraic (both sufficient and necessary) conditions are derived. Due to their longtime modetransitional behavior, which is very difficult to predict, only partial results are obtained for the Ttime observable states. Nevertheless, we completely resolve the Ttime local observability for the bimodal conewise linear system, for finite T, and provide numerical examples to illustrate the difficulty associated with the longtime observability.