Approximately counting semismooth integers

  • Authors:
  • Eric Bach;Jonathan P. Sorenson

  • Affiliations:
  • University of Wisconsin, Madison, WI, USA;Butler University, Indianapolis, IN, USA

  • Venue:
  • Proceedings of the 38th international symposium on International symposium on symbolic and algebraic computation
  • Year:
  • 2013

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Abstract

An integer n is (y,z)-semismooth if n=pm where m is an integer with all prime divisors ≥ y and p is 1 or a prime ≥ z. Large quantities of semismooth integers are utilized in modern integer factoring algorithms, such as the number field sieve, that incorporate the so-called large prime variant. Thus, it is useful for factoring practitioners to be able to estimate the value of Ψ(x,y,z), the number of (y,z)-semismooth integers up to x, so that they can better set algorithm parameters and minimize running times, which could be weeks or months on a cluster supercomputer. In this paper, we explore several algorithms to approximate Ψ(x,y,z) using a generalization of Buchstab's identity with numeric integration.