Jacobi/Legendre/Kronecker

[Torbjorn Granlund]

nisse at lysator.liu.se (Niels Möller) writes:

  I don't have the time to investigate carefully right now, but some
  comments:
  
  The functions mpz_kronecker_ui and mpz_ui_kronecker have not been
  updated in years. They call mpn_jacobi_base to do the main work.
  mpn_jacobi_base is implemented in a couple of different ways, one new
  and several older. Tuning should select the fastest one, via
  JACOBI_BASE_METHOD, with 4 being the new and usually faster code.
  
  mpz_jacobi and mpz_legendre are aliases for the same function. That has
  been completely rewritten in 5.1, calling the new mpn_jacobi_n function
  for larger operands, and mpn_jacobi_base directly if the smaller operand
  fits in a limb. 20% difference for single-limb operands definitely is
  disturbing, I don't see what that might come from.
  
I'd suggest that we hold the release until at least the weekend, to see
if some of us have time and inspiration to fix this.

Speed regressions are never fun.  Small operands are the most important
ones, of course.

-- 
Torbjörn