Code Submition ( Improvement for mpn_mul_fft )

[Jeunder Yu]

> How does the speed compare between the old and new code?  In the
> GMP world, speed is all that counts, of course.  :-)

CPU: Pentium 4 2.6GHz
RAM: 512MB

Two operands are 2^n limbs with random value.

size    old     new
====================
n=13   0.013   0.011
n=14   0.031   0.027
n=15   0.072   0.064
n=16   0.160   0.145
n=17   0.374   0.348
n=18   0.824   0.767
n=19   1.682   1.441
n=20   3.398   2.845
n=21   7.252   6.053
n=22  16.625  13.957
n=23  34.203  29.497
n=24 408.061 350.596
(virtual memory swap in/out for n>=24)

Is this comparison enough?

> -- 
> Torbjörn