Niels Möller nisse at lysator.liu.se
Mon Jul 5 19:28:52 UTC 2021

Torbjörn Granlund <tg at gmplib.org> writes:

> I suppose it would be somewhat interesting to know how close the
> measured best and measured 2nd best methods are, or how much better the
> measured best methods is than the configured method.

Part 1 is done by the "runner up" logic I added to tuneup a while ago. In
the tuneup output, it looks like 

#define DIV_QR_1N_PI1_METHOD                 4  /* 13.42% faster than 2 */

(example from
But not surfaced in an obvious way on the threshold web pages. 

Part 2 would be relevant too, in particular when the configured method
is neither best or the runner up, according to tuneup.

> And, when there is asm, the scary performance ratio between C and asm
> which would suggest that C-to-C comparisons of tight GMP loops might not
> be terribly relevant.  :-)

That's a more subtle comparison. Would also be good to annotate which C
method (if any) the assembly routine is based on.


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