Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.python > #81100
| Path | csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed2.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail |
|---|---|
| Return-Path | <python-python-list@m.gmane.org> |
| X-Original-To | python-list@python.org |
| Delivered-To | python-list@mail.python.org |
| X-Spam-Status | OK 0.001 |
| X-Spam-Evidence | '*H*': 1.00; '*S*': 0.00; 'algorithm': 0.04; 'inspired': 0.05; 'root': 0.05; 'sys': 0.07; 'calculating': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'def': 0.12; 'math,': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'true:': 0.16; 'valueerror': 0.16; 'wrote:': 0.18; 'import': 0.22; 'header:User-Agent:1': 0.23; 'integer': 0.24; 'header:X-Complaints-To:1': 0.27; 'header:In- Reply-To:1': 0.27; 'raise': 0.29; "d'aprano": 0.31; 'steven': 0.31; 'there': 0.35; 'positive': 0.37; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'charset:windows-1252': 0.65; 'received:46': 0.66; 'here': 0.66; 'optimized': 0.68; 'square': 0.74; 'ideas.': 0.84 |
| X-Injected-Via-Gmane | http://gmane.org/ |
| To | python-list@python.org |
| From | Serhiy Storchaka <storchaka@gmail.com> |
| Subject | Re: Challenge: optimizing isqrt |
| Date | Thu, 20 Nov 2014 20:00:04 +0200 |
| References | <54543787$0$13005$c3e8da3$5496439d@news.astraweb.com> |
| Mime-Version | 1.0 |
| Content-Type | text/plain; charset=windows-1252; format=flowed |
| Content-Transfer-Encoding | 7bit |
| X-Gmane-NNTP-Posting-Host | 46.211.151.127 |
| User-Agent | Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.0 |
| In-Reply-To | <54543787$0$13005$c3e8da3$5496439d@news.astraweb.com> |
| X-BeenThere | python-list@python.org |
| X-Mailman-Version | 2.1.15 |
| Precedence | list |
| List-Id | General discussion list for the Python programming language <python-list.python.org> |
| List-Unsubscribe | <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe> |
| List-Archive | <http://mail.python.org/pipermail/python-list/> |
| List-Post | <mailto:python-list@python.org> |
| List-Help | <mailto:python-list-request@python.org?subject=help> |
| List-Subscribe | <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.16037.1416506494.18130.python-list@python.org> (permalink) |
| Lines | 34 |
| NNTP-Posting-Host | 2001:888:2000:d::a6 |
| X-Trace | 1416506494 news.xs4all.nl 2937 [2001:888:2000:d::a6]:49605 |
| X-Complaints-To | abuse@xs4all.nl |
| Xref | csiph.com comp.lang.python:81100 |
Show key headers only | View raw
On 01.11.14 03:29, Steven D'Aprano wrote:
> There is an algorithm for calculating the integer square root of any
> positive integer using only integer operations:
Here is my optimized implementation inspired by Christian's ideas.
import math, sys
C1 = sys.float_info.radix ** sys.float_info.mant_dig
C2 = int(sys.float_info.max)
C3 = C2.bit_length() - 2
def isqrt(n):
if n < 0:
raise ValueError
if n == 0:
return 0
if n <= C1:
return int(math.sqrt(n))
if n <= C2:
x = int(math.sqrt(n))
else:
b = (n.bit_length() - C3) // 2
x = int(math.sqrt(n >> (2 * b))) << b
y = (x + n // x) // 2
if y == x:
return x
while True:
x = y
y = (x + n // x) // 2
if y >= x:
return x
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Challenge: optimizing isqrt Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-01 12:29 +1100
Re: Challenge: optimizing isqrt Chris Angelico <rosuav@gmail.com> - 2014-11-01 13:12 +1100
Re: Challenge: optimizing isqrt Christian Gollwitzer <auriocus@gmx.de> - 2014-11-01 09:02 +0100
Re: Challenge: optimizing isqrt Christian Gollwitzer <auriocus@gmx.de> - 2014-11-01 09:09 +0100
Re: Challenge: optimizing isqrt Chris Angelico <rosuav@gmail.com> - 2014-11-01 19:13 +1100
Re: Challenge: optimizing isqrt Christian Gollwitzer <auriocus@gmx.de> - 2014-11-01 09:25 +0100
Re: Challenge: optimizing isqrt Chris Angelico <rosuav@gmail.com> - 2014-11-01 19:33 +1100
Re: Challenge: optimizing isqrt Christian Gollwitzer <auriocus@gmx.de> - 2014-11-01 09:38 +0100
Re: Challenge: optimizing isqrt Chris Angelico <rosuav@gmail.com> - 2014-11-01 19:45 +1100
Re: Challenge: optimizing isqrt Akira Li <4kir4.1i@gmail.com> - 2014-11-01 12:12 +0300
Re: Challenge: optimizing isqrt Serhiy Storchaka <storchaka@gmail.com> - 2014-11-20 20:00 +0200
Re: Challenge: optimizing isqrt Stephen Tucker <stephen_tucker@sil.org> - 2014-11-21 08:15 +0000
Re: Challenge: optimizing isqrt Dave Angel <davea@davea.name> - 2014-11-23 10:43 -0500
Re: Challenge: optimizing isqrt Serhiy Storchaka <storchaka@gmail.com> - 2014-11-25 21:31 +0200
Re: Challenge: optimizing isqrt Dave Angel <davea@davea.name> - 2014-11-25 19:46 -0500
Re: Challenge: optimizing isqrt Stephen Tucker <stephen_tucker@sil.org> - 2014-11-26 07:57 +0000
Re: Challenge: optimizing isqrt Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-11-26 21:25 +1100
Re: Challenge: optimizing isqrt Serhiy Storchaka <storchaka@gmail.com> - 2014-11-26 18:24 +0200
csiph-web