Q-adic transform revisited

  • Authors:
  • Jean-Guillaume Dumas

  • Affiliations:
  • Université de Grenoble, Grenoble, France

  • Venue:
  • Proceedings of the twenty-first international symposium on Symbolic and algebraic computation
  • Year:
  • 2008

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Abstract

We present an algorithm to perform a simultaneous modular reduction of several residues. This enables to compress polynomials into integers and perform several modular operations with machine integer arithmetic. The idea is to convert the X-adic representation of modular polynomials, with X an indeterminate, to a q-adic representation where q is an integer larger than the field characteristic. With some control on the different involved sizes it is then possible to perform some of the q-adic arithmetic directly with machine integers or floating points. Depending also on the number of performed numerical operations one can then convert back to the q-adic or X-adic representation and eventually mod out high residues. In this note we present a new version of both conversions: more tabulations and a way to reduce the number of divisions involved in the process are presented. The polynomial multiplication is then applied to arithmetic and linear algebra in small finite field extensions.