GMP 4.3 multiplication performance

[Torbjorn Granlund]

David Harvey <dmharvey at cims.nyu.edu> writes:

  One case in which I am particularly interested is the 2n * n
  unbalanced multiplication. This should be no more expensive than
  twice the cost of an n * n multiplication, plus O(n) overhead that
  should be negligible for large n.
  
I think it should be slightly cheaper than twice the cost of two n * n
multiplications.

  But here is what I get for current 4.3 stable (changeset 85a941ada149
  checked out this morning, on core 2 duo, mac OS X, after running
  tuneup, using the attached python script). Columns are n, cost for
  2n*n mult, cost for two n*n mults, ratio.
  
[snip table]
  
  The numbers around 700-3000 limbs are not good.
  
Thanks, this was an eye opening comparison.

Let's address this for GMP 4.4!

-- 
Torbjörn