[Python-Dev] Numerical robustness, IEEE etc.

Nick Maclaren nmm1 at cus.cam.ac.uk
Fri Jun 23 10:13:17 CEST 2006

"Neal Norwitz" <nnorwitz at gmail.com> wrote:
> Seriously, there seems to be a fair amount of miscommunication in this
> thread.  ...

Actually, this isn't really a reply to you, but you have described
the issue pretty well.

> The best design doc that I know of is code. :-)
> It would be much easier to communicate using code snippets.
> I'd suggest pointing out places in the Python code that are lacking
> and how you would correct them.  That will make it easier for everyone
> to understand each other.

Yes.  That is easy.  What, however, I have part of (already) and was
proposing to do BEFORE going into details was to generate a testing
version that shows how I think that it should be done.  Then people
could experiment with both the existing code and mine, to see the

But, in order to do that, I needed to find out the best way of going
about it ....

It wouldn't help with the red herrings, such as the reasons why it
is no longer possible to rely on hardware interrupts as a mechanism.
But they are only very indirectly relevant.

The REASON that I wanted to do that was precisely because I knew that
very few people would be deeply into arithmetic models, the details
of C89 and C99 (ESPECIALLY as the standard is incomplete :-( ), and
so having a sandbox before starting the debate would be a GREAT help.
It's much easier to believe things when you can try them yourself ....

"Facundo Batista" <facundobatista at gmail.com> wrote:
> Well, so I'm completely lost... because, if all you want is to be able
> to chose a returned value or an exception raised, you actually can
> control that in Decimal.

Yes, but I have so far failed to get hold of a copy of the Decimal code!
I will have another go at subverting Subversion.  I should VERY much
like to be get hold of those documents AND build a testing version of
the code - then I can go away, experiment, and come back with some more
directed comments (not mere generalities).

Aahz <aahz at pythoncraft.com> wrote:
> You can't expect us to do your legwork for you, and you can't expect
> that Tim Peters is the only person on the dev team who understands what
> you're getting at.

Well, see above for the former - I did post my intents in my first
message.  And, as for the latter, I have tried asking what I can
assume that people know - it is offensive and time-consuming and hence
counter-productive to start off assuming that your audience does not
have a basic background.

To repeat, it is precisely to address THAT issue that I wanted to build
a sandbox BEFORE going into details.  If people don't know the theory
in depth and but are interested, they could experiment with the sandbox
and see what happens in practice.

> Incidentally, your posts will go directly to python-dev without
> moderation if you subscribe to the list, which is a Good Idea if you want
> to participate in discussion.

Er, you don't receive a mailing list at all if you don't subscribe!

If that is the intent, I will see if I can find how to subscribe in
the unmoderated fashion.  I didn't spot two methods on the Web pages
when I subscribed.

Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email:  nmm1 at cam.ac.uk
Tel.:  +44 1223 334761    Fax:  +44 1223 334679

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