I'm trying to understand some unexpected behaviour with float NANs in
Python 3.5.
Background: in IEEE-754 maths, NANs (Not A Number) come in two flavours,
so called "quiet NANs" and "signalling NANs". By default, arithmetic
operations on qnans return a qnan; operations on snans "signal", which
09.11.18 13:05, Steven D'Aprano пише:
py> x = cast_int2float(0x7ff1)
py> x
nan
py> hex(cast_float2int(x))
'0x7ff80001'
I got '0x7ff1'.
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works for me, too:
In [9]: x = cast_int2float(0x7ff80001)
In [10]: hex(cast_float2int(x))
Out[10]: '0x7ff80001'
In [11]: x = cast_int2float(0x7ff1)
In [12]: hex(cast_float2int(x))
Out[12]: '0x7ff1'
OS-X, conda build:
Python 3.7.0 | packaged by conda-forge
On Fri, Nov 09, 2018 at 01:17:09PM -0800, Chris Barker via Python-Dev wrote:
> works for me, too:
>
> In [9]: x = cast_int2float(0x7ff80001)
> In [10]: hex(cast_float2int(x))
> Out[10]: '0x7ff80001'
>
> In [11]: x = cast_int2float(0x7ff1)
> In [12]: hex(cast_float2int(
On Sat, Nov 10, 2018 at 3:26 PM, Steven D'Aprano wrote:
> On Fri, Nov 09, 2018 at 01:17:09PM -0800, Chris Barker via Python-Dev wrote:
>> works for me, too:
>>
>> In [9]: x = cast_int2float(0x7ff80001)
>> In [10]: hex(cast_float2int(x))
>> Out[10]: '0x7ff80001'
>>
>> In [11]: x = c
On Sat, Nov 10, 2018 at 04:27:29PM -0800, Nathaniel Smith wrote:
> Apparently loading a sNaN into an x87 register silently converts it to
> a qNaN, and on Linux C compilers are allowed to do that at any point:
>
>
> https://stackoverflow.com/questions/22816095/signalling-nan-was-corrupted-whe
Steven D'Aprano wrote:
The Debian box uses an ARM processor, so there's that difference too.
FWIW, I tried this on MacOSX 10.6 with an Intel Xeon and it also
seems to suppress sNaNs.
--
Greg
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