Searching Worst Cases of a One-Variable Function Using Lattice Reduction

Damien Stehlé 1 Paul Zimmermann 1 Vincent Lefèvre 1
1 SPACES - Solving problems through algebraic computation and efficient software
INRIA Lorraine, LORIA - Laboratoire Lorrain de Recherche en Informatique et ses Applications
Abstract : We propose a new algorithm to find worst cases for the correct rounding of a mathematical function of one variable. We first reduce this problem to the real small value problem—i.e., for polynomials with real coefficients. Then, we show that this second problem can be solved efficiently by extending Coppersmith's work on the integer small value problem—for polynomials with integer coefficients—using lattice reduction. For floating-point numbers with a mantissa less than N and a polynomial approximation of degree d, our algorithm finds all worst cases at distance less than N^{\frac{-d^2}{2d+1}} from a machine number in time O(N^{{\frac{d+1}{2d+1}}+\varepsilon}). For d=2, a detailed study improves on the O(N^{2/3+\varepsilon}) complexity from Lefèvre's algorithm to O(N^{4/7+\varepsilon}). For larger d, our algorithm can be used to check that there exist no worst cases at distance less than N^{-k} in time O(N^{1/2+\varepsilon}).
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https://hal.inria.fr/inria-00000379
Contributor : Damien Stehle <>
Submitted on : Thursday, September 29, 2005 - 5:52:31 PM
Last modification on : Thursday, January 11, 2018 - 6:20:00 AM

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Damien Stehlé, Paul Zimmermann, Vincent Lefèvre. Searching Worst Cases of a One-Variable Function Using Lattice Reduction. IEEE Transactions on Computers, Institute of Electrical and Electronics Engineers, 2005, 54 (3), pp.340-346. ⟨10.1109/TC.2005.55⟩. ⟨inria-00000379⟩

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