Improving Goldschmidt Division, Square Root, and Square Root Reciprocal

  • Authors:
  • Milos D. Ercegovac;Laurent Imbert;David W. Matula;Jean-Michel Muller;Guoheng Wei

  • Affiliations:
  • Univ. of California at Los Angeles, Los Angeles;Univ. de Provence, Marseille, France;Southern Methodist Univ., Dallas, TX;Ecole Normale Supérieure de Lyon, Lyon, France;Southern Methodist Univ., Dallas, TX

  • Venue:
  • IEEE Transactions on Computers - Special issue on computer arithmetic
  • Year:
  • 2000

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Abstract

The aim of this paper is to accelerate division, square root, and square root reciprocal computations when the Goldschmidt method is used on a pipelined multiplier. This is done by replacing the last iteration by the addition of a correcting term that can be looked up during the early iterations. We describe several variants of the Goldschmidt algorithm, assuming 4-cycle pipelined multiplier, and discuss obtained number of cycles and error achieved. Extensions to other than 4-cycle multipliers are given. If we call $G_m$ the Goldschmidt algorithm with $m$ iterations, our variants allow us to reach an accuracy that is between that of $G_3$ and that of $G_4$, with a number of cycle equal to that of $G_3$.