[Python-Dev] Numerical robustness, IEEE etc.

Facundo Batista facundobatista at gmail.com
Tue Jun 20 20:25:26 CEST 2006

2006/6/20, Nick Coghlan <ncoghlan at gmail.com>:

> Nick Maclaren wrote:
> > Brett Cannon's and Neal Norwitz's replies appreciated and noted, but
> > responses sent by mail.

Damn, the most difficult way to keep a thread...

> The intent was always to replace the internal use of tuples and longs with a
> more efficient C implementation - that particular step simply wasn't needed
> for the original use case that lead Facundo to write and implement PEP 327.

Right. We never addressed speed. I mean, we made Decimal as fast as we
could in the limited time we had (Raymond H. helped a lot also here),
but it was NOT designed for speed.

BTW, prove me Decimal is not fast enough, ;)

> Mateusz Rucowicz has taken up the challenge for Google's Summer of Code
> (mentored by Facundo Batista, the original author of PEP 327 and the decimal
> module).
> I've cc'ed Facundo, so hopefully he will see this thread and chime in :)

I was reading the thread, yes, but it's so difficult to follow when
half the messages are not in the list... :(

> > Mode A:  follow IEEE 754R slavishly, if and when it ever gets into print.
> > There is no point in following C99, as it is too ill-defined, even if it
> > were felt desirable.  This should not be the default, because of the
> > flaws I mention above (see Kahan on Java).

See Cowlishaw's specification for how you can configure contexts to
achieve different "modes", and reasons for it and all.

Easier way: Just read Decimal docs.

> Let's not skip it, because the decimal module already seems to do pretty much
> what you describe here :)

Well... I think I missed it... but a very good way to resume it would
be: Explain us what do you need to do that there's not achievable with


.    Facundo

Blog: http://www.taniquetil.com.ar/plog/
PyAr: http://www.python.org/ar/

More information about the Python-Dev mailing list