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Groups > comp.lang.python > #91211
| From | Christian Gollwitzer <auriocus@gmx.de> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: a more precise distance algorithm |
| Date | 2015-05-25 22:27 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <mk00gr$kku$1@dont-email.me> (permalink) |
| References | <b2e66a94-7a89-4be9-bbf7-9434396cc178@googlegroups.com> |
Am 25.05.15 um 21:21 schrieb ravas: > I read an interesting comment: > """ > The coolest thing I've ever discovered about Pythagorean's Theorem is an alternate way to calculate it. If you write a program that uses the distance form c = sqrt(a^2 + b^2) you will suffer from the lose of half of your available precision because the square root operation is last. A more accurate calculation is c = a * sqrt(1 + b^2 / a^2). If a is less than b, you should swap them and of course handle the special case of a = 0. > """ > > Is this valid? Yes. Valid for floating point math, which can overflow and lose precision. > Does it apply to python? Yes. Python uses floating point math by default > Any other thoughts? :D > > My imagining: > > def distance(A, B): Wrong. Just use the built-in function Math.hypot() - it should handle these cases and also overflow, infinity etc. in the best possible way. Apfelkiste:~ chris$ python Python 2.7.2 (default, Oct 11 2012, 20:14:37) [GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import math >>> math.hypot(3,4) 5.0 Christian
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a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 12:21 -0700
Re: a more precise distance algorithm felix <felix@epepm.cupet.cu> - 2015-05-25 16:06 -0400
Re: a more precise distance algorithm Christian Gollwitzer <auriocus@gmx.de> - 2015-05-25 22:27 +0200
Re: a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 14:03 -0700
Re: a more precise distance algorithm Gary Herron <gary.herron@islandtraining.com> - 2015-05-25 13:20 -0700
Re: a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 14:05 -0700
Re: a more precise distance algorithm Steven D'Aprano <steve@pearwood.info> - 2015-05-26 13:11 +1000
Re: a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 21:13 -0700
Re: a more precise distance algorithm Gary Herron <gherron@digipen.edu> - 2015-05-25 22:09 -0700
Re: a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 22:49 -0700
Re: a more precise distance algorithm Christian Gollwitzer <auriocus@gmx.de> - 2015-05-26 07:33 +0200
Re: a more precise distance algorithm Brian Blais <bblais@gmail.com> - 2015-05-27 14:00 -0400
Re: a more precise distance algorithm Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-05-27 23:03 +0100
Re: a more precise distance algorithm Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-05-27 23:04 -0400
Re: a more precise distance algorithm Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-25 22:42 -0600
Re: a more precise distance algorithm ravas <ravas@outlook.com> - 2015-05-25 21:59 -0700
Re: a more precise distance algorithm random832@fastmail.us - 2015-05-26 09:40 -0400
Re: a more precise distance algorithm random832@fastmail.us - 2015-05-26 09:51 -0400
Re: a more precise distance algorithm Robin Becker <robin@reportlab.com> - 2015-05-27 14:02 +0100
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