[Ironpython-users] IronPython float_info values (was: IronPython always in 32-bit mode on 64bit machine even when running ipy64.exe)

Mon May 13 16:16:54 CEST 2013

Hi,

Is anyone with commit access willing to commit the fix? And possibly include it in the upcoming 2.7.4? :-)

Thanks :-)

Best regards

Markus Schaber

CODESYS(r) a trademark of 3S-Smart Software Solutions GmbH

Inspiring Automation Solutions

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Dipl.-Inf. Markus Schaber | Product Development Core Technology
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> Von: Jeff Hardy [mailto:jdhardy at gmail.com]
> Gesendet: Freitag, 10. Mai 2013 18:15
> An: Markus Schaber
> Cc: ironpython-users at python.org
> Betreff: Re: [Ironpython-users] IronPython float_info values (was:
> IronPython always in 32-bit mode on 64bit machine even when running
> ipy64.exe)
> 
> For me, using BitConverter.IsLittleEndian is clearer:
> 
>   private static readonly double EPSILON =
> System.BitConverter.Int64BitsToDouble(
>     System.BitConverter.IsLittleEndian ? 0x3cb0000000000000 :
> 0x000000000000b03c);
> 
>   private static readonly double MIN =
> System.BitConverter.Int64BitsToDouble(
>     System.BitConverter.IsLittleEndian ? 0x0010000000000000 :
> 0x0000000000001000);
> 
> I don't think half-endian machines are worth worrying about. :)
> 
> - Jeff
> 
> 
> On Fri, May 10, 2013 at 1:41 AM, Markus Schaber
> <m.schaber at codesys.com> wrote:
> > Hi,
> >
> >
> >
> > Maybe we'd use some conditional initializiation, checking for the
> > properties of the number, like the following:
> >
> >
> >
> >         // The definition of Epsion and MinValue differ
> between .NET
> > and Python/C,
> >
> >         // so we need to define our own values.
> >
> >         // Approx. -2.2204460492503131e-16 - the byte order
> reversed
> > value is approx.
> >
> >         // 2.2290265677773679e-319, so this code delivers the
> correct
> > value independently
> >
> >         // of the byte order of the machine.
> >
> >         private static readonly double EPSILON = Math.Max(
> >
> >
> System.BitConverter.Int64BitsToDouble(0x3cb0000000000000),
> >
> >
> > System.BitConverter.Int64BitsToDouble(0x000000000000b03c));
> >
> >         // Approx. 2.2250738585072014e-308 - the byte-order
> reversed
> > value is approx.
> >
> >         // 2.0236928853657458e-320, so this code delviers the
> correct
> > value independently
> >
> >         // of the byte order of the machine.
> >
> >         private static readonly double MIN = Math.Max(
> >
> >
> System.BitConverter.Int64BitsToDouble(0x0010000000000000),
> >
> >
> > System.BitConverter.Int64BitsToDouble(0x0000000000001000));
> >
> >
> >
> >         public static floatinfo float_info = new
> > floatinfo(Double.MaxValue, 1024, 308, MIN, -1021, -307, 15, 53,
> > EPSILON, 2, 1);
> >
> >
> >
> > This trick relies on the fact that for the given values, the
> reversed
> > byte order produces an zero-Exponent, which are denormalized
> numbers,
> > and in both cases, the wanted number is a normalized one which (by
> > definition) is larger than the denormalized one.
> >
> >
> >
> > This code is as elegant as checking for the endianness explicitly,
> and
> > we are even safe for machines where the integer and float
> endianness
> > are different (see
> > https://en.wikipedia.org/wiki/Endianness#Floating-
> point_and_endianness
> > - although I doubt that those hardware is relevant for our user
> base...)
> > J
> >
> >
> >
> >
> >
> >
> >
> > Best regards
> >
> > Markus Schaber
> >
> > CODESYS(r) a trademark of 3S-Smart Software Solutions GmbH
> >
> > Inspiring Automation Solutions
> >
> > ________________________________
> >
> > 3S-Smart Software Solutions GmbH
> > Dipl.-Inf. Markus Schaber | Product Development Core Technology
> > Memminger Str. 151 | 87439 Kempten | Germany Tel. +49-831-54031-979
> |
> > Fax +49-831-54031-50
> >
> > E-Mail: m.schaber at codesys.com | Web: codesys.com | CODESYS store:
> > store.codesys.com
> > CODESYS forum: forum.codesys.com
> >
> > Managing Directors: Dipl.Inf. Dieter Hess, Dipl.Inf. Manfred Werner
> |
> > Trade
> > register: Kempten HRB 6186 | Tax ID No.: DE 167014915
> >
> > Von: Slide [mailto:slide.o.mix at gmail.com]
> > Gesendet: Mittwoch, 8. Mai 2013 22:44
> > An: Jeff Hardy
> > Cc: Markus Schaber; Curt Hagenlocher; ironpython-users at python.org
> >
> >
> > Betreff: Re: [Ironpython-users] IronPython float_info values (was:
> > IronPython always in 32-bit mode on 64bit machine even when running
> > ipy64.exe)
> >
> >
> >
> > Unless Microsoft really wants pain and anguish, they are likely
> > running in little endian mode. I've never run across an ARM setup
> that
> > actually runs in big endian (nor do I want to), so I'm pretty sure
> its
> > little endian. I'd be more than willing to test an app on my phone
> > since Windows Phone is crap anyway, so you couldn't damage it any
> > worse than it is now :-)
> >
> >
> >
> > Alex
> >
> >
> >
> > On Wed, May 8, 2013 at 12:54 PM, Jeff Hardy <jdhardy at gmail.com>
> wrote:
> >
> > On Wed, May 8, 2013 at 9:15 AM, Markus Schaber
> <m.schaber at codesys.com>
> > wrote:
> >> Hi,
> >>
> >>
> >>
> >
> >> The main problem for now is that I can't test whatever solution we
> >> find, because I don't have access to any hardware with non-intel
> Byte
> >> Order and a Microsoft .NET. (I don't want to rely on Mono for this
> >> test...)
> >
> > Is ARM big-endian? If so, any Windows 8 ARM tablet (i.e. Surface RT)
> > or Windows Phone should do. Heck, even the emulator might do. It
> > shouldn't be too hard to whip up an app that prints those two
> values,
> > and I think Alex has a Windows Phone if he'd be willing to test it.
> >
> > If ARM is little-endian (or Windows/ARM runs in little-endian mode)
> > then I don't think it matters; we'd have to try Mono on a PowerPC
> or
> > something like that.
> >
> > - Jeff
> >
> >
> >
> >
> >
> > --
> > Website: http://earl-of-code.com
> >
> >
> > _______________________________________________
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> >