Cancellation with hgcd / unbalanced mulmod_bnm1

[Torbjorn Granlund]

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

  Torbjorn Granlund <tg at gmplib.org> writes:
  
  > I think you forgot the save-the-transform trick.
  > Since b is implicitly invariant over several a_i pieces,
  > evaluating b once will be a slight win.
  
  That's a bit difficult to do with current interfaces, though. And I
  suspect that for this non-extreme unbalancedness, toom42/62/63 is a
  better strategy.
  
With toom62 we need quite large operands due to costs for the
interpolation.

Perhaps one should look into a specialised toom-like primitive that
directly takes the cancellation into account?  This should not be hard
to investigate.

-- 
Torbjörn