On 27 May 2015 at 19:00, Brian Blais wrote:
> On Mon, May 25, 2015 at 11:11 PM, Steven D'Aprano wrote:
>>
>> Let's compare three methods.
>>
>> def naive(a, b):
>> return math.sqrt(a**2 + b**2)
>>
>> def alternate(a, b):
>> a, b = min(a, b), max(a, b)
>> if a == 0: return b
>> if
On Mon, May 25, 2015 at 11:11 PM, Steven D'Aprano wrote:
>
> Let's compare three methods.
>
> def naive(a, b):
> return math.sqrt(a**2 + b**2)
>
> def alternate(a, b):
> a, b = min(a, b), max(a, b)
> if a == 0: return b
> if b == 0: return a
> return a * math.sqrt(1 + b**2 /
A minor point is that if you just need to compare distances you don't need to
compute the hypotenuse, its square will do so no subtractions etc etc.
--
Robin Becker
--
https://mail.python.org/mailman/listinfo/python-list
On Tue, May 26, 2015, at 09:40, random...@fastmail.us wrote:
> On Mon, May 25, 2015, at 15:21, ravas wrote:
> > Is this valid? Does it apply to python?
> > Any other thoughts? :D
>
> The math.hypot function uses the C library's function which should deal
> with such concerns internally. There is a
On Mon, May 25, 2015, at 15:21, ravas wrote:
> Is this valid? Does it apply to python?
> Any other thoughts? :D
The math.hypot function uses the C library's function which should deal
with such concerns internally. There is a fallback version in case the C
library does not have this function, in P
On Monday, May 25, 2015 at 10:16:02 PM UTC-7, Gary Herron wrote:
> It's probably not the square root that's causing the inaccuracies. In
> many other cases, and probably here also, it's the summing of two
> numbers that have vastly different values that loses precision. A
> demonstration:
>
>
Am 26.05.15 um 05:11 schrieb Steven D'Aprano:
mismatch after 3 trials
naive: 767.3916150255787
alternate: 767.3916150255789
hypot: 767.3916150255787
which shows that:
(1) It's not hard to find mismatches;
(2) It's not obvious which of the three methods is more accurate.
The main problem is
On 05/25/2015 09:13 PM, ravas wrote:
On Monday, May 25, 2015 at 8:11:25 PM UTC-7, Steven D'Aprano wrote:
Let's compare three methods.
...
which shows that:
(1) It's not hard to find mismatches;
(2) It's not obvious which of the three methods is more accurate.
Thank you; that is very helpful!
Oh ya... true >_<
Thanks :D
On Monday, May 25, 2015 at 9:43:47 PM UTC-7, Ian wrote:
> > def distance(A, B):
> > """
> > A & B are objects with x and y attributes
> > :return: the distance between A and B
> > """
> > dx = B.x - A.x
> > dy = B.y - A.y
> > a = min(dx, dy)
On Mon, May 25, 2015 at 1:21 PM, ravas wrote:
> I read an interesting comment:
> """
> The coolest thing I've ever discovered about Pythagorean's Theorem is an
> alternate way to calculate it. If you write a program that uses the distance
> form c = sqrt(a^2 + b^2) you will suffer from the lose
On Monday, May 25, 2015 at 8:11:25 PM UTC-7, Steven D'Aprano wrote:
> Let's compare three methods.
> ...
> which shows that:
>
> (1) It's not hard to find mismatches;
> (2) It's not obvious which of the three methods is more accurate.
Thank you; that is very helpful!
I'm curious: what about the
On Tue, 26 May 2015 05:21 am, ravas wrote:
> I read an interesting comment:
> """
> The coolest thing I've ever discovered about Pythagorean's Theorem is an
> alternate way to calculate it. If you write a program that uses the
> distance form c = sqrt(a^2 + b^2) you will suffer from the lose of ha
On Monday, May 25, 2015 at 1:27:43 PM UTC-7, Gary Herron wrote:
> This is a statement about floating point numeric calculations on a
> computer,. As such, it does apply to Python which uses the underlying
> hardware for floating point calculations.
>
> Validity is another matter. Where did yo
On Monday, May 25, 2015 at 1:27:24 PM UTC-7, Christian Gollwitzer wrote:
> Wrong. Just use the built-in function Math.hypot() - it should handle
> these cases and also overflow, infinity etc. in the best possible way.
>
> Apfelkiste:~ chris$ python
> Python 2.7.2 (default, Oct 11 2012, 20:14:37)
Am 25.05.15 um 21:21 schrieb ravas:
I read an interesting comment:
"""
The coolest thing I've ever discovered about Pythagorean's Theorem is an
alternate way to calculate it. If you write a program that uses the distance
form c = sqrt(a^2 + b^2) you will suffer from the lose of half of your
av
On 05/25/2015 12:21 PM, ravas wrote:
I read an interesting comment:
"""
The coolest thing I've ever discovered about Pythagorean's Theorem is an
alternate way to calculate it. If you write a program that uses the distance
form c = sqrt(a^2 + b^2) you will suffer from the lose of half of your
a
El 25/05/15 15:21, ravas escribió:
I read an interesting comment:
"""
The coolest thing I've ever discovered about Pythagorean's Theorem is an
alternate way to calculate it. If you write a program that uses the distance
form c = sqrt(a^2 + b^2) you will suffer from the lose of half of your
ava
I read an interesting comment:
"""
The coolest thing I've ever discovered about Pythagorean's Theorem is an
alternate way to calculate it. If you write a program that uses the distance
form c = sqrt(a^2 + b^2) you will suffer from the lose of half of your
available precision because the square r
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