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[Python-Dev] Python on non IEEE-754 platforms: plea for information.

Mark Dickinson dickinsm at gmail.com
Fri Feb 1 23:52:13 CET 2008 
A request for information:

What non IEEE 754 platforms exist that people care about running Python 2.6,
Python 3.0 and higher on?
By non IEEE 754 platform, I mean a platform where either the C double is not
the usual 64-bit IEEE floating-point format, or where the C double is IEEE
format but the platform deviates in major ways from the IEEE 754
specification.  There are a few places (mostly in mathmodule.c,
cmathmodule.c, floatobject.c, longobject.c) where it's not clear that the
code behaves correctly on non-IEEE platforms, and I'm finding it difficult
to determine how broken (or not) it is without having a clear idea of what
possible unusual floating-point formats might come up.
The major non-IEEE floating-point formats that I know of, on big iron, are
the VAX, Cray and IBM formats;  I believe anything else is too old to worry
about.  Is this true?  The IBM format is particularly troublesome because
it's base 16 instead of base 2 (so e.g. multiplying a float by 2 can lose
bits), but it appears that recent IBM machines do both IBM format and IEEE
format floating-point.  I assume that the S-390 buildbots are using the IEEE
side---is this true?

At the other end of the spectrum are embedded devices and cellphones.  Here
I have no idea what the situation is at all---any information would be
valuable.

Mark
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