Even faster integer multiplication David Harvey, Joris van der Hoeven, Grégoire Lecerf To cite this version: David Harvey, Joris van der Hoeven, Grégoire Lecerf. Even faster integer multiplication. 2014. hal- 01022749v2 HAL Id: hal-01022749 https://hal.archives-ouvertes.fr/hal-01022749v2 Preprint submitted on 11 Feb 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Even faster integer multiplication David Harvey Joris van der Hoevena, Grégoire Lecerfb School of Mathematics and Statistics CNRS, Laboratoire d’informatique University of New South Wales École polytechnique Sydney NSW 2052 91128 Palaiseau Cedex Australia France Email:
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[email protected] February 11, 2015 We give a new proof of Fürer’s bound for the cost of multiplying n-bit integers in the bit complexity model. Unlike Fürer, our method does not require constructing special coefficient ∗ rings with “fast” roots of unity. Moreover, we establish the improved bound O(n lognKlog n) with K = 8. We show that an optimised variant of Fürer’s algorithm achieves only K = 16, ∗ suggesting that the new algorithm is faster than Fürer’s by a factor of 2log n.