[Python-Dev] Python 2.6/3.0, IEEE 754 floating point semantics and S60 (original) (raw)

Christian Heimes christian at cheimes.de
Thu Nov 27 15:58:43 CET 2008

A while ago I contacted Jukka Laurila from the Nokia developer board about IEEE 754 support on S60 phones. The information from Jukka may be useful for future reference.

Christian

-------- Original Message -------- Subject: Re: Python 2.6/3.0, IEEE 754 floating point semantics and S60

We've been battling with some float problems recently as well in the course of our 2.5 core porting. The principal problem has been imprecise floating point formatting/parsing routines which lead to the unfortunate case of not being able to roundtrip a Python float to string and back bit-exactly. I've been trying to get to the bottom of that problem and so far it seems like the root cause is a poorly written C library.

Though on the other hand, no one from Symbian is yet to confirm to me that the software-emulated floating point routines correspond to anything like IEEE 754. Most S60 devices lack floating point hardware.

The best guess is that the floating point support is IEEE 754'ish, with imprecise formatting and parsing routines in the standard library.

-Jukka

On 2.2.2008 3.54, "ext Crys @ Developer Discussion Boards"

This is a message from Crys at Developer Discussion Boards ( http://discussion.forum.nokia.com/forum/index.php ). The Developer Discussion Boards owners cannot accept any responsibility for the contents of the email.

To email Crys, you can use this online form: http://discussion.forum.nokia.com/forum/sendmessage.php?do=mailmember&u=187359 This is the message: Hallo jplauril! I'm a Python core developer. Mikko Ohtamaa said that I should contact you about this matter. Mark Dickinson and I are working on several math and floating point related enhancements for Python 2.6 and 3.0. The enhancements include better support for IEEE754 style NaN and INF, C99 math functions and consistent errors and return values across platforms. Can you give use some detailed information about how Nokia's S60 series processes and stores double precision floats? Information about Qtopia would be useful as well. See http://permalink.gmane.org/gmane.comp.python.devel/91591 Your's truly Christian Heimes

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