On Fri, Feb 24, 2017 at 6:43 PM, Nathaniel Smith wrote:
> On Feb 24, 2017 5:29 PM, "David Mertz" wrote:
>
> Marc-André slightly misspelled the recent-ish addition of math.isclose(),
> but I agree that it is absolutely where a "nextafter" belongs.
>
>
> My 2c: I disagree -- numerical tolerance b
I do agree that a math.count_ulps() would be very nice to have. Or whatever
spelling NumPy users for that concept.
I see nextafter as more similar. Yes, it's not a uniform increment, which
is the whole point. If you want a convergence that is as good as it can be
in float, that's the relevant meas
On 25 February 2017 at 12:43, Nathaniel Smith wrote:
> FWIW, numpy provides all of the following as separate functions:
>
> * an isclose equivalent
> * nextafter
> * a function for counting the number of ulps between two floats
> * a function for checking that two floats differ by at most N ulps
On Feb 24, 2017 5:29 PM, "David Mertz" wrote:
Marc-André slightly misspelled the recent-ish addition of math.isclose(),
but I agree that it is absolutely where a "nextafter" belongs.
The function signature is already relatively complex to cover several
different but related use cases. I.e.:
Marc-André slightly misspelled the recent-ish addition of math.isclose(),
but I agree that it is absolutely where a "nextafter" belongs.
The function signature is already relatively complex to cover several
different but related use cases. I.e.:
is_close(a, b, *, rel_tol=1e-09, abs_tol=0.0)
On Feb 24, 2017, at 10:28 AM, Mahmoud Hashemi wrote:
By the way, it looks like math doesn't have machine epsilon either:
>
>
> https://en.wikipedia.org/wiki/Machine_epsilon
>
> Pretty sure machine epsilon is in the sys module's float_info object.
Ahh, thanks! I though I remembered it was somewh
By the way, it looks like math doesn't have machine epsilon either:
>
>
> https://en.wikipedia.org/wiki/Machine_epsilon
>
> which would be handy as well.
>
> -CHB
>
>
Pretty sure machine epsilon is in the sys module's float_info object. Or
are you saying it would be handy to alias sys.float_info.ep
On Fri, Feb 24, 2017 at 1:40 AM, Juraj Sukop wrote:
>
>
> On Fri, Feb 24, 2017 at 5:01 AM, Chris Barker
> wrote:
>
>> cause if your computation was that perfect, why not just check for zero?
>>
>>
> A polynomial root may simply be not representable in double precision
> floating-point format.
>
On 24.02.2017 10:13, Nick Coghlan wrote:
> On 6 February 2017 at 20:29, M.-A. Lemburg wrote:
>
>> On 04.02.2017 12:59, Stephan Houben wrote:
>>> Hi all,
>>>
>>> Visual C++ 2015 supports this one:
>>>
>>> https://msdn.microsoft.com/en-us/library/h0dff77w.aspx
>>>
>>> In any case, this is easy to i
On Fri, Feb 24, 2017 at 5:01 AM, Chris Barker wrote:
> cause if your computation was that perfect, why not just check for zero?
>
>
A polynomial root may simply be not representable in double precision
floating-point format. Per the example I posted above, the best one can
hope for in such situat
On 6 February 2017 at 20:29, M.-A. Lemburg wrote:
> On 04.02.2017 12:59, Stephan Houben wrote:
> > Hi all,
> >
> > Visual C++ 2015 supports this one:
> >
> > https://msdn.microsoft.com/en-us/library/h0dff77w.aspx
> >
> > In any case, this is easy to implement an efficient fallback in C, unlike
>
On Mon, Feb 6, 2017 at 5:42 AM, Juraj Sukop wrote:
> Do you mean something like:
>
> isclose(f(x), 0.0, rel_tol, abs_tol)
>
> If so, what should `rel_tol` and `abs_tol` be?
>
isclose is mostly about "relative" closeness, so rel_tol is more-or-less
the number of decimal digits you want the s
On Sat, Feb 4, 2017, at 10:15, Steve Dower wrote:
> These days, the subset of C99 supported by MSVC is "most" of it, so feel
> free to start off by assuming the best, at least for new features (the
> version we use for 2.7 obviously is not improving).
The subset of the C *library*, anyway, since i
On 07.02.2017 00:46, Steven D'Aprano wrote:
> On Mon, Feb 06, 2017 at 11:29:17AM +0100, M.-A. Lemburg wrote:
>
>> I'm not sure how useful this would be in the stdlib,
>> since it's very much tied to whatever float type Python
>> happens to use on a platform.
>
> With the possible exception of µPy
On Mon, Feb 06, 2017 at 11:29:17AM +0100, M.-A. Lemburg wrote:
> I'm not sure how useful this would be in the stdlib,
> since it's very much tied to whatever float type Python
> happens to use on a platform.
With the possible exception of µPy, are there any Python implementations
which don't use
Do you mean something like:
isclose(f(x), 0.0, rel_tol, abs_tol)
If so, what should `rel_tol` and `abs_tol` be?
On Mon, Feb 6, 2017 at 2:16 PM, M.-A. Lemburg wrote:
> On 06.02.2017 13:22, Juraj Sukop wrote:
> > On Mon, Feb 6, 2017 at 11:29 AM, M.-A. Lemburg wrote:
> >
> >>
> >> Juraj: Cou
On 06.02.2017 13:22, Juraj Sukop wrote:
> On Mon, Feb 6, 2017 at 11:29 AM, M.-A. Lemburg wrote:
>
>>
>> Juraj: Could you provide some use cases, where such a function
>> would help in Python applications ? (I can see use cases
>> written in C, but due to the low level, find it hard to
>> believe
On Mon, Feb 6, 2017 at 11:29 AM, M.-A. Lemburg wrote:
>
> Juraj: Could you provide some use cases, where such a function
> would help in Python applications ? (I can see use cases
> written in C, but due to the low level, find it hard to
> believe that people would use this at the Python level)
>
On 04.02.2017 12:59, Stephan Houben wrote:
> Hi all,
>
> Visual C++ 2015 supports this one:
>
> https://msdn.microsoft.com/en-us/library/h0dff77w.aspx
>
> In any case, this is easy to implement an efficient fallback in C, unlike
> the fma() function we discussed some time ago.
>
> To put this i
"tritium-l...@sdamon.com"
Sent: 2/4/2017 3:53
To: "python-ideas@python.org"
Subject: Re: [Python-ideas] math.nextafter
The presence of the function in C99’s math.h isn’t strictly useful unless it is
also in the MSVC math.h. MSVC only supports a subset of C99
From: Python-ideas
rom:* Python-ideas [mailto:python-ideas-bounces+tritium-list=sdamon.com@
> python.org] *On Behalf Of *Juraj Sukop
> *Sent:* Saturday, February 4, 2017 6:31 AM
> *To:* python-ideas@python.org
> *Subject:* [Python-ideas] math.nextafter
>
>
>
> Hello!
>
>
>
> Function `nextafter
To: python-ideas@python.org
Subject: [Python-ideas] math.nextafter
Hello!
Function `nextafter(x, y)` returns the next representable value of `x` in the
direction of `y`, and if `x` equals to `y`, `y` is returned. [1]
It is useful for incrementing/decrementing floating-point number by
Hello!
Function `nextafter(x, y)` returns the next representable value of `x` in
the direction of `y`, and if `x` equals to `y`, `y` is returned. [1]
It is useful for incrementing/decrementing floating-point number by the
smallest amount possible or for testing if two numbers are closest to each
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