[CLN-list] CLN 1.2.0

[Joerg Arndt]

* Richard B. Kreckel <kreckel at ginac.de> [Jan 22. 2008 13:08]:
> Joerg Arndt wrote:
>>>> May I suggest to add a AGM based pi-computation?
>>> Well, patches are very welcome!  ;-)
>> I'll give it a try.
>> Here is why I suggested it:
>> Some people compare performance of Pi computations
>> ignoring that one is AGM based and another is binsplit
>> based.  Having both gives a good impression on the
>> performance of these two fundamentally different
>> (and fundamentally important) algorithms.
>
> Good idea. Where, approximately, do you expect a break-even to occur? 
> Should we make bets?

binsplit wins routinely whenever applicable, mostly for its memory
locality.  There are, however, things where (to my knowledge) no
binsplit based algorithm can be used.  So it is fine to also know
about the performance of the AGM.

No bets, but you may want to smash 15 secs (AGM!) for 1 mio digits
of Pi (hfloat, after 50% speedup with recursive FHT, see fxtbook
if not yet there in CLN).

AGM based algorithms spent >95% (sometimes 99%) in the transforms
so you do get a fine impression about your raw multiplication speed
(if the AGM is properly done).  All assuming you are using very
large precisions.  Only if you know your code very well you can
make _any_ guess about the speed (and still you might be far off).

>
>   -richy.

Btw. example programs make learning easy, especially for people
who check the doc only if everything else fails  8-))

If the example programs have a timing mechanism then they are
also usable to detect regressions with performance.


cheers,   jj