Division call in mpn_gcd

Torbjorn Granlund tg at gmplib.org
Sat Feb 25 14:00:54 CET 2012

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

  > Perhaps this is the reason for keeping redc separate?
  IIRC, bdiv functions return a borrow, meaning that the remainder
  corresponding to the computed quotient is negative, while red returns a
  carry which means that the computed remainder is a bit too large.
That redc behaviour is just one week old...

  And then the questions was if a remainder-only function should follow
  the redc convention, since that's the most important use, or the bdiv_qr
  convention, for consistency.
And we shouldn't sacrifice speed for consistency, at the lowest mpn

  > Really?  Doesn't that quotient affect the cofactors?
  It affects one of the cofactors: the one which we're not going to
I see.  I suppose that means the caller that really wants the cofactor
should performs this initial (Hensel) division, for efficiency.


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