Accurate Evaluation of Polynomials in Legendre Basis

作者:Du, Peibing*; Jiang, Hao; Cheng, Lizhi
来源:Journal of Applied Mathematics, 2014, 2014: 742538.
DOI:10.1155/2014/742538

摘要

This paper presents a compensated algorithm for accurate evaluation of a polynomial in Legendre basis. Since the coefficients of the evaluated polynomial are fractions, we propose to store these coefficients in two floating point numbers, such as double-double format, to reduce the effect of the coefficients' perturbation. The proposed algorithm is obtained by applying error-free transformation to improve the Clenshaw algorithm. It can yield a full working precision accuracy for the ill-conditioned polynomial evaluation. Forward error analysis and numerical experiments illustrate the accuracy and efficiency of the algorithm.