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Ming Tian - One of the best experts on this subject based on the ideXlab platform.

Fumiaki Kohsaka - One of the best experts on this subject based on the ideXlab platform.

Siwen Jiao - One of the best experts on this subject based on the ideXlab platform.

Hideaki Iiduka - One of the best experts on this subject based on the ideXlab platform.

  • acceleration of the halpern algorithm to search for a fixed point of a nonexpansive mapping
    Fixed Point Theory and Applications, 2014
    Co-Authors: Kaito Sakurai, Hideaki Iiduka
    Abstract:

    This paper presents an algorithm to accelerate the Halpern fixed point algorithm in a real Hilbert space. To this goal, we first apply the Halpern algorithm to the smooth Convex Minimization Problem, which is an example of a fixed point Problem for a nonexpansive mapping, and indicate that the Halpern algorithm is based on the steepest descent method for solving the Minimization Problem. Next, we formulate a novel fixed point algorithm using the ideas of conjugate gradient methods that can accelerate the steepest descent method. We show that, under certain assumptions, our algorithm strongly converges to a fixed point of a nonexpansive mapping. We numerically compare our algorithm with the Halpern algorithm and show that it dramatically reduces the running time and iterations needed to find a fixed point compared with that algorithm. MSC:47H10, 65K05, 90C25.

  • Acceleration method for Convex optimization over the fixed point set of a nonexpansive mapping
    Mathematical Programming, 2014
    Co-Authors: Hideaki Iiduka
    Abstract:

    The existing algorithms for solving the Convex Minimization Problem over the fixed point set of a nonexpansive mapping on a Hilbert space are based on algorithmic methods, such as the steepest descent method and conjugate gradient methods, for finding a minimizer of the objective function over the whole space, and attach importance to minimizing the objective function as quickly as possible. Meanwhile, it is of practical importance to devise algorithms which converge in the fixed point set quickly because the fixed point set is the set with the constraint conditions that must be satisfied in the Problem. This paper proposes an algorithm which not only minimizes the objective function quickly but also converges in the fixed point set much faster than the existing algorithms and proves that the algorithm with diminishing step-size sequences strongly converges to the solution to the Convex Minimization Problem. We also analyze the proposed algorithm with each of the Fletcher---Reeves, Polak---Ribiere---Polyak, Hestenes---Stiefel, and Dai---Yuan formulas used in the conventional conjugate gradient methods, and show that there is an inconvenient possibility that their algorithms may not converge to the solution to the Convex Minimization Problem. We numerically compare the proposed algorithm with the existing algorithms and show its effectiveness and fast convergence.

  • weak convergence of a projection algorithm for variational inequalities in a banach space
    Journal of Mathematical Analysis and Applications, 2008
    Co-Authors: Hideaki Iiduka, Wataru Takahashi
    Abstract:

    Abstract Let C be a nonempty, closed Convex subset of a Banach space E. In this paper, motivated by Alber [Ya.I. Alber, Metric and generalized projection operators in Banach spaces: Properties and applications, in: A.G. Kartsatos (Ed.), Theory and Applications of Nonlinear Operators of Accretive and Monotone Type, in: Lecture Notes Pure Appl. Math., vol. 178, Dekker, New York, 1996, pp. 15–50], we introduce the following iterative scheme for finding a solution of the variational inequality Problem for an inverse-strongly-monotone operator A in a Banach space: x 1 = x ∈ C and x n + 1 = Π C J −1 ( J x n − λ n A x n ) for every n = 1 , 2 , … , where Π C is the generalized projection from E onto C, J is the duality mapping from E into E ∗ and { λ n } is a sequence of positive real numbers. Then we show a weak convergence theorem (Theorem 3.1). Finally, using this result, we consider the Convex Minimization Problem, the complementarity Problem, and the Problem of finding a point u ∈ E satisfying 0 = A u .

Yekini Shehu - One of the best experts on this subject based on the ideXlab platform.