Browsing by Author "Vu, Phuong Ahn"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A Memoryless Augmented Gauss-Newton Method for Nonlinear Least-Squares Problems
    (1985-02) Dennis, J.E. Jr.; Songbai, Sheng; Vu, Phuong Ahn
    In this paper, we develop, analyze, and test a new algorithm for nonlinear least-squares problems. The algorithm uses a BFGS update of the Gauss-Newton Hessian when some heuristics indicate that the Gauss-Newton method may not make a good step. Some important elements are that the secant or quasi-Newton equations considered are not the obvious ones, and the method does not build up a Hessian approximation over several steps. The algorithm can be implemented easily as a modification of any Gauss-Newton code, and it seems to be useful for large residual problems
  • Thumbnail Image
    Item
    A New Nonlinear Equations Test Problem
    (1983-06) Dennis, J.E. Jr.; Gay, David M.; Vu, Phuong Ahn
    This presents a set of test problems for nonlinear equations and nonlinear least-squares algorithms. These problems, sent to us by C.V. Nelson of the Maine Medical Center, come from a dipole model of the heart. They are 6 x 6 or 8 x 8, easy to code, cheap to evaluate, and not easy to solve. In support of the latter contention, we present test results from MINPACK AND NL2SOL.