A more accurate Briggs method for the logarithm

  • Authors:
  • Awad H. Al-Mohy

  • Affiliations:
  • Department of Mathematics, King Khalid University, Abha, Saudi Arabia

  • Venue:
  • Numerical Algorithms
  • Year:
  • 2012

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Abstract

A new approach for computing an expression of the form $a^{1/2^k}-1$ is presented that avoids the danger of subtractive cancellation in floating point arithmetic, where a is a complex number not belonging to the closed negative real axis and k is a nonnegative integer. We also derive a condition number for the problem. The algorithm therefore allows highly accurate numerical calculation of log(a) using Briggs' method.