new Toom-Cook 3-way code

[Torbjorn Granlund]

[Background to gmp-devel readers: Paul just made improvements to
the toom3 multiply code, and is now working on gcd.  I've been
suggesting that we extend the low-level mpn functions with some
combined operations like shift-add and shift-sub.]

Paul.Zimmermann@loria.fr (Paul Zimmermann) writes:

     A different question is whether to extend the low level function
     set somewhat.  E.g., mpn_addmul_1 could be complemented with
     mpn_addmul_2exp (or if we choose to call it mpn_addlsh).
     (Analogously with mpn_submul_2exp/mpn_sublsh.)
  
     If a += 2b is in practice the only power-of-2 multiplier that
     will be used, perhaps we could implement just that.  I expect
     that to be faster on x86 then a general mpn_addmul_2exp.
  
  A general mpn_addlsh (for a shift 0 <= k < GMP_NUMB_BITS) would be
  highly welcome, especially in the mpfr addition.
  
  Here are some first results on the gcd front:
  
  norroy% ./gcd 50000 # 50000-limbs numbers
  mpz_gcdnew took 6580ms
  mpz_gcd took 34260ms
  
This is great news.  You're busy hacking GMP these days!

When it comes to gcd, please coordinate with nisse@lysator.liu.se.
He recently mailed new code to gmp-devel@swox.com.
(I am ashamed to say that nobody reacted to his posting yet.)

-- 
Torbjörn