Re: A missing (?) function: exponentfp(x)

On 19/09/2024 06:30, Ilya Zakharevich wrote:
> On Wed, Sep 18, 2024 at 10:38:09AM +0200, Aurel Page wrote:
>> ? install("exponentfp","G");
>> ? exponentfp(2^30-1)
>> %2 = 29.999999998656385002
>> ? exponentfp(Pi)
>> %3 = 1.6514961294723207175
>> ? z = Pi*2^20
>> %4 = 3294198.6583305710348142047482656880163
>> ? for(i=1,10^6,exponent(z))
>> cpu time = 276 ms, real time = 276 ms.
>> ? for(i=1,10^6,exponentfp(z))
>> cpu time = 312 ms, real time = 312 ms.
> Hard to tell: on my (more than a decade old, cheap) laptop, the code
> with exponent() takes 78 ms — but only 15 ms of them is taken by
> exponent() itself.  Rescaling proportionally, this would make
> exponentfp() twice as slow exponent() — which, if true, would be
> REALLY GREAT!  Thanks!
>
> However, to estimate THE REAL power of this, one needs to know the
> timing of
>
>     ? for(i=1,10^6,(z))
>
> (but I would redo everything with 10^8 — on some architectures
> sub-0.1-seconds timing is not fully reliable…)5~
>
> A Lot of Thanks again,
> Ilya
>
>    P.S.  Looking into the source, it probably does not support non-real
>    	types; does it?
>
> 	For best results, it should better propagate better to other
>    	types: fold()-by-max() for vectors/etc, fallback-to-exponent()
>    	for non-real numeric types (etc?)…
Yes, this was a proof-of-concept, we can of course propagate it to other 
types.

Cheers,
Aurel