A path-following algorithm is proposed for finding a solution to the nonlinear stationary point problem on an unbounded, convex, and pointed polyhedron. The algorithm can start at an arbitrary point of the polyhedron....
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A path-following algorithm is proposed for finding a solution to the nonlinear stationary point problem on an unbounded, convex, and pointed polyhedron. The algorithm can start at an arbitrary point of the polyhedron. The path to be followed by the algorithm is described as the path of zeros of some piecewise continuously differentiable function defined on an appropriate subdivided manifold. This manifold is induced by a generalized primal-dual pair of subdivided manifolds. The path of zeros can be approximately followed by dividing the polyhedron into simplices and replacing the original function by its piecewise linear approximation with respect to this subdivision. The piecewise linear path of this function can be generated by alternating replacement steps and linear programming pivot steps. A condition under which the path of zeros converges to a solution is also stated, and a description of how the algorithm operates when the problem is linear or when the polyhedron is the Cartesian product of a polytope and an unbounded polyhedron is given.
A triangulation of the nonnegative orthant and a special labeling of the vertices lead to a combinatorial procedure for seeking solutions or approximate solutions to the nonlinear complementarity problem under coerciv...
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In this paper we propose a variable dimension simplicial algorithm for solving the variational inequality problem on the cross product of the nonnegative orthant ℝ+m of the m-dimensional Euclidean space ℝm and the n-d...
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The well-known Tarski’s fixed point theorem asserts that an increasing mapping from an n-dimensional box to itself has a fixed point. In this paper, a constructive proof of this theorem is obtained from an applicatio...
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The well-known Tarski’s fixed point theorem asserts that an increasing mapping from an n-dimensional box to itself has a fixed point. In this paper, a constructive proof of this theorem is obtained from an application of the (n+1)-ray arbitrary starting simplicial algorithm. The algorithm assigns an integer label to each point of the box and employs a triangulation to subdivide the box into simplices. For any given mesh size of the triangulation, starting from an arbitrary interior point of the box, the algorithm generates within a finite number of iterations a complete n-dimensional simplex, any point of which yields an approximate fixed point. If the accuracy is not good enough, the mesh size of the triangulation is refined and the algorithm is restarted. When the mesh size goes to zero sequentially, one will obtain a sequence of approximate fixed points satisfying that every limit point of the sequence is a fixed point.
Ideas of a simplicial variable dimension restart algorithm to approximate zero points onR n developed by the authors and of a linear complementarity problem pivoting algorithm are combined to an algorithm for solvin...
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Ideas of a simplicial variable dimension restart algorithm to approximate zero points onR n developed by the authors and of a linear complementarity problem pivoting algorithm are combined to an algorithm for solving the nonlinear complementarity problem with lower and upper bounds. The algorithm can be considered as a modification of the2n-ray zero point finding algorithm onR n . It appears that for the new algorithm the number of linear programming pivot steps is typically less than for the2n-ray algorithm applied to an equivalent zero point problem. This is caused by the fact that the algorithm utilizes the complementarity conditions on the variables.
In this paper we compare the efficiency of several simplicial variable dimension algorithms. To do so, we first treat the issues of degeneracy and accelerating. We present a device for solving degeneracy. Furthermore ...
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In this paper we compare the efficiency of several simplicial variable dimension algorithms. To do so, we first treat the issues of degeneracy and accelerating. We present a device for solving degeneracy. Furthermore we compare several accelerating techniques. The technique of iterated quasi-Newton steps after each major cycle of the simplicial algorithm is implemented in a computer code, which is used to compare the efficiency of the (n+1)-ray, 2n-ray, 2n-ray and (3n−1)-ray algorithms. Except for the (n+1)-ray algorithm, the number of function evaluations does not differ very much between the various algorithms. It appeared, however, that the 2n-algorithm needs considerably less computation time.
In this paper three sufficient conditions are provided under each of which an upper semicontinuous point-to-set mapping defined on an arbitrary polytope has a connected set of zero points that connect two distinct fac...
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In this paper three sufficient conditions are provided under each of which an upper semicontinuous point-to-set mapping defined on an arbitrary polytope has a connected set of zero points that connect two distinct faces of the polytope. Furthermore, we obtain an existence theorem of a connected set of solutions to a nonlinear variational inequality problem over arbitrary polytopes. These results follow in a constructive way by designing a new simplicial algorithm. The algorithm operates on a triangulation of the polytope and generates a piecewise linear path of points connecting two distinct faces of the polytope. Each point on the path is an approximate zero point. As the mesh size of the triangulation goes to zero, the path converges to a connected set of zero points linking the two distinct faces. As a consequence, our results generalize Browder's fixed point theorem [ Summa Brasiliensis Mathematicae, 4 (1960), pp. 183-191] and an earlier result by the authors [ Math. Oper. Res., 21 (1996), pp. 675-696] on the n-dimensional unit cube. An application in economics and some numerical examples are also discussed.
In this paper we establish the existence of a discrete zero point of a function from the n-dimensional integer lattice Z(n) to the n-dimensional Euclidean space R-n under very general conditions with respect to the be...
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In this paper we establish the existence of a discrete zero point of a function from the n-dimensional integer lattice Z(n) to the n-dimensional Euclidean space R-n under very general conditions with respect to the behavior of the function. The proof is constructive and uses a combinatorial argument based on a simplicial algorithm with vector labeling and lexicographic linear programming pivot steps. The algorithm provides an efficient method to find an exact solution. We also discuss how to adapt the algorithm for two related problems, namely, to find a discrete zero point of a function under a general antipodal condition and to find a solution to a discrete nonlinear complementarity problem. In both cases the modified algorithm provides a constructive existence proof, too. We further show that the algorithm for the discrete nonlinear complementarity problem generalizes the well-known Lemke's method to nonlinear environments. An economic application is also presented.
We study nonlinear variational inequality problems over polytopes from a viewpoint of stability and propose a new solution concept. Extending an earlier concept proposed by Yang [Z. Yang, SIAM J. Control Optim., 34 (1...
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We study nonlinear variational inequality problems over polytopes from a viewpoint of stability and propose a new solution concept. Extending an earlier concept proposed by Yang [Z. Yang, SIAM J. Control Optim., 34 (1996), pp. 491-506] on the unit simplex, we will introduce the concept of the robust stationary point, which is a refinement of the concept of the stationary point. Though a stationary point need not be robust, it is shown that every continuous function on a polytope has a robust stationary point. We develop a simplicial algorithm to compute a robust stationary point of a continuous function on a polytope. The algorithm can be briefly stated as follows. Starting with any point in the relative interior of a polytope, the algorithm generates a piecewise linear path which leads to an approximate robust stationary point of any a priori chosen accuracy within a finite number of steps. Moreover, we also discuss several numerical examples and apply the new concept to noncooperative games and economic equilibrium problems.
In this paper we present two theorems on the existence of a discrete zero point of a function from the n-dimensional integer lattice Z(n) to the n-dimensional Euclidean space R-n. The theorems differ in their boundary...
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In this paper we present two theorems on the existence of a discrete zero point of a function from the n-dimensional integer lattice Z(n) to the n-dimensional Euclidean space R-n. The theorems differ in their boundary conditions. For both theorems we give a proof using a combinatorial lemma and present a constructive proof based on a simplicial algorithm that finds a discrete zero point within a finite number of steps.
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