"Terry Reedy" <[EMAIL PROTECTED]> writes:
> "Grant Edwards" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > I'm working on it. I should have said it's trivial if you have
> > access to the platforms to be supported. I've tested a fix
> > that supports pickle streams generated
Robert Kern wrote:
>
> And floating point is about nothing if not being usefully wrong.
>
+1 QOTW and maybe it could be worked into the FAQ about floats as well :-)
http://www.python.org/doc/faq/general.html#why-are-floating-point-calculations-so-inaccurate
Kent
--
http://mail.python.org/mailm
Tim Peters wrote:
> OK, I looked, and it made no difference to me. Really. If I had an
> infinitely tall monitor, maybe I could see a difference, but I don't
> -- the sign of 0 on the nose makes no difference to the behavior of
> 1/x for any x other than 0. On my finite monitor, I see it looks
Tim Peters wrote:
> [Steven D'Aprano]
>>It isn't necessary to look at complex numbers to see the difference
>>between positive and negative zero. Just look at a graph of y=1/x. In
>>particular, look at the behaviour of the graph around x=0. Now tell me
>>that the sign of zero doesn't make a differ
Hi All--
Tim Peters wrote:
> Fortran is so
> eager to allow optimizations that failure due to numeric differences
> in conformance tests rarely withstood challenge.
+1 QOTW
Metta,
Ivan
--
Ivan Van Laningham
God N Locomotive Works
http://www.andi-holmes
[Tim Peters']
>> Well, I try, Ivan. But lest the point be missed , 754 doesn't
>> _want_ +0 and -0 to act differently in "almost any" way. The only
>> good rationale I've seen for why it makes the distinction at all is in
>> Kahan's paper "Branch Cuts for Complex
>> Elementary Functions, or Much
On Thu, 23 Jun 2005 00:11:20 -0400, Tim Peters wrote:
> Well, I try, Ivan. But lest the point be missed , 754 doesn't
> _want_ +0 and -0 to act differently in "almost any" way. The only
> good rationale I've seen for why it makes the distinction at all is in
> Kahan's paper "Branch Cuts for Comp
[Tim Peters]
...
>> Across platforms with a 754-conforming libm, the most portable way [to
>> distinguish +0.0 from -0.0 in standard C] is via using atan2(!):
>>
>> >>> pz = 0.0
>> >>> mz = -pz
>> >>> from math import atan2
>> >>> atan2(pz, pz)
>> 0.0
>> >>> atan2(mz, mz)
>> -3.1415926535897931
[I
Hi All--
Tim Peters wrote:
> Across platforms with a 754-conforming
> libm, the most portable way is via using atan2(!):
>
> >>> pz = 0.0
> >>> mz = -pz
> >>> from math import atan2
> >>> atan2(pz, pz)
> 0.0
> >>> atan2(mz, mz)
> -3.1415926535897931
>
Never fails. Tim, you gave me the best la
On 2005-06-23, Grant Edwards <[EMAIL PROTECTED]> wrote:
> On 2005-06-23, Tim Peters <[EMAIL PROTECTED]> wrote:
>
>> C89 doesn't define the result of that, but "most" C compilers these
>> days will create a negative 0.
>>
>>> and (double)0x8000 doesn't work,
>
> I think you meant something like
On 2005-06-23, Tim Peters <[EMAIL PROTECTED]> wrote:
> C89 doesn't define the result of that, but "most" C compilers these
> days will create a negative 0.
>
>> and (double)0x8000 doesn't work,
I think you meant something like
float f;
*((uint32_t*)&d) = 0x;
>> And I don't know
On 2005-06-23, Paul Rubin wrote:
> Scott David Daniels <[EMAIL PROTECTED]> writes:
>> >>>Negative 0 isn't a NaN, it's just negative 0.
>> >>
>> >>Right, but it is hard to construct in standard C.
>> > Huh? It's just a hex constant.
>> Well, -0.0 doesn't work, and (double)0x8000 doesn't work,
On 2005-06-22, Paul Rubin wrote:
>>> Negative 0 isn't a NaN, it's just negative 0.
>>
>> Right, but it is hard to construct in standard C.
>
> Huh? It's just a hex constant.
Yup. There are two ways to construct a NaN. One is to do
something like (1e300*1e300)/(1e300*1e300) and hope for the
be
On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
> Grant Edwards wrote:
>> On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>>>Several issues:
>>
>>
>>>(1) The number of distinct NaNs varies among platforms.
>>
>> According to the IEEE standard, there are exactly two:
>
Scott David Daniels <[EMAIL PROTECTED]> writes:
> >>>Negative 0 isn't a NaN, it's just negative 0.
> >>
> >>Right, but it is hard to construct in standard C.
> > Huh? It's just a hex constant.
> Well, -0.0 doesn't work, and (double)0x8000 doesn't work,
> and I think you have to use quirks
[with the start of US summer comes the start of 754 ranting season]
[Grant Edwards]
Negative 0 isn't a NaN, it's just negative 0.
[Scott David Daniels]
>>> Right, but it is hard to construct in standard C.
[Paul Rubin]
>> Huh? It's just a hex constant.
[Scott David Daniels]
> Well, -0.0 d
Paul Rubin wrote:
> Scott David Daniels <[EMAIL PROTECTED]> writes:
>
>>>Negative 0 isn't a NaN, it's just negative 0.
>>
>>Right, but it is hard to construct in standard C.
>
>
> Huh? It's just a hex constant.
Well, -0.0 doesn't work, and (double)0x8000 doesn't work,
and I think you ha
Scott David Daniels <[EMAIL PROTECTED]> writes:
> > Negative 0 isn't a NaN, it's just negative 0.
> Right, but it is hard to construct in standard C.
Huh? It's just a hex constant.
--
http://mail.python.org/mailman/listinfo/python-list
Grant Edwards wrote:
> On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>>Several issues:
>
>
>>(1) The number of distinct NaNs varies among platforms.
>
> According to the IEEE standard, there are exactly two:
> signalling and quiet, and on platforms that don't impliment
> floating
"Grant Edwards" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> The bit patterns are defined by the IEEE 754 standard. If
> there are Python-hosting platoforms that don't use IEEE 754 as
> the floating point representation, then that can be dealt with.
>
> Python has _tons_ of plat
On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>> I'm working on it. I should have said it's trivial if you have
>> access to the platforms to be supported. I've tested a fix
>> that supports pickle streams generated under Win32 and glibc.
>> That's using the "native" string repre
"Grant Edwards" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I'm working on it. I should have said it's trivial if you have
> access to the platforms to be supported. I've tested a fix
> that supports pickle streams generated under Win32 and glibc.
> That's using the "native" s
Grant Edwards wrote:
> I'm working on it. I should have said it's trivial if you have
> access to the platforms to be supported. I've tested a fix
> that supports pickle streams generated under Win32 and glibc.
> That's using the "native" string representation of a NaN or
> Inf.
Several issues:
(
On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>> Fixing it is really quite trivial. It takes less than a dozen
>> lines of code. Just catch the exception and handle it.
>
> Since you know it is quite trivial, and I don't, why not
> submit a patch resolving this issue. Be sure to
Grant Edwards wrote:
> On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>>>...Under Win32, the pickle module only works with a subset of
>>> floating point values. In particular ... infinity or nan ...
>>
>>There is no completely portable way to do this.
>
> Python deals with all sor
On 2005-06-22, Scott David Daniels <[EMAIL PROTECTED]> wrote:
>> I finally figured out why one of my apps sometimes fails under
>> Win32 when it always works fine under Linux: Under Win32, the
>> pickle module only works with a subset of floating point
>> values. In particular the if you try to d
Grant Edwards wrote:
> I finally figured out why one of my apps sometimes fails under
> Win32 when it always works fine under Linux: Under Win32, the
> pickle module only works with a subset of floating point
> values. In particular the if you try to dump/load an infinity
> or nan value, the load
On 2005-06-21, Grant Edwards <[EMAIL PROTECTED]> wrote:
> I finally figured out why one of my apps sometimes fails under
> Win32 when it always works fine under Linux
[...]
Oh, I forgot, here's pickletest.py:
#!/usr/bin/python
import pickle
f1 = (1e300*1e300)
f2 = f1/f1
o = (f1,f2)
s = pickle.d
I finally figured out why one of my apps sometimes fails under
Win32 when it always works fine under Linux: Under Win32, the
pickle module only works with a subset of floating point
values. In particular the if you try to dump/load an infinity
or nan value, the load operation chokes:
Under Lin
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