An in-place truncated Fourier transform and applications to polynomial multiplication

(with Daniel Roche)

Proceedings of the 2010 International Symposium on Symbolic and Algebraic Computation (ISSAC 2010), Munich, pages 325–329 (DOI).

arXiv preprint (January 2010).

Abstract

The truncated Fourier transform (TFT) was introduced by van der Hoeven in 2004 as a means of smoothing the “jumps” in running time of the ordinary FFT algorithm that occur at power-of-two input sizes. However, the TFT still introduces these jumps in memory usage. We describe in-place variants of the forward and inverse TFT algorithms, achieving time complexity O(n log n) with only O(1) auxiliary space. As an application, we extend the second author's results on space-restricted FFT-based polynomial multiplication to polynomials of arbitrary degree.


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