[MPFR] multiplications vs. subtractions: which one is faster?

[Patrick Pelissier]

> Thank you Patrick. However I'd like to point out that those figures (I mean
> the ratio of the number of cycles for both variants) might vary from one
> platform to the other, maybe by more than a factor of two. They might also
> depend on the version of mpfr, on the fact that GMP and/or MPFR were tuned
> for that platform, and on the actual operand values (in particular mpfr_sub
> might be slower when subtracting numbers that are very close).

Yes.
Moreover, I expect the subtraction version to be faster on Pentium 4,
whereas the multiplication version should be faster on opteron/amd64.

--
  Patrick Pélissier