Toom-8 testing (mpz level)

[Niels Möller]

Torbjorn Granlund <tg at gmplib.org> writes:

> nisse at lysator.liu.se (Niels Möller) writes:
>
>   The region where base case wins looks like bn < THRESHOLD, which is
>   nice. I.e., it could use a threshold on the size of the smaller factor
>   only.
>   
> Yes, but also notice the little tongue of basecase-blue between toom22
> and toom32, and the larger tongue between toom32 and toom42.

I wonder how large the performance difference is in those tongues. If
it's just a percent or two, I wouldn't care too much. And if it's
more, then one might consider a more or less complete table for
algorithm choice for sizes up to 30 limbs or so (BTW, it would be nice
if you could add some numbers to the axes of the figures. It's hard to
see on  the logarithmic plots what the operand sizes falls within
these tongues.

There's also a a tongue or two where toom62 partial sticks down into
the area of small bn, otherwise owned by schoolbook. Most visible on
the (logarithmic) Core i7 plot. Any explanation for that?

Regards,
/Niels