Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #48699

Re: Why is regex so slow?

Show all headers | View raw

On 18.06.2013 22:30, Grant Edwards wrote:

> All the O() tells you is the general shape of the line.

Nitpick: it only gives an *upper bound* for the complexity. Any function
that is within O(n) is also within O(n^2). Usually when people say O()
they actually mean capital Thetha (which is the correct term).

> It's perfectly
> feasible that for the range of values of n that you care about in a
> particular application, there's an O(n^2) algorithm that's way faster
> than another O(log(n)) algorithm.  [Though that becomes a lot less
> likely as n gets large.]

Since O() only gives upper bounds it's also possible for an algorithm
within O(n^2) to always be faster than another algorithm within O(logn).
The O(n^2) algorithm could be Thetha(1).

Regards,
Johannes

-- 
>> Wo hattest Du das Beben nochmal GENAU vorhergesagt?
> Zumindest nicht öffentlich!
Ah, der neueste und bis heute genialste Streich unsere großen
Kosmologen: Die Geheim-Vorhersage.
 - Karl Kaos über Rüdiger Thomas in dsa <hidbv3$om2$1@speranza.aioe.org>

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Why is regex so slow? roy@panix.com (Roy Smith) - 2013-06-18 12:45 -0400
  Re: Why is regex so slow? Skip Montanaro <skip@pobox.com> - 2013-06-18 12:01 -0500
  Re: Why is regex so slow? Roy Smith <roy@panix.com> - 2013-06-18 13:08 -0400
  Re: Why is regex so slow? Chris Angelico <rosuav@gmail.com> - 2013-06-19 03:20 +1000
    Re: Why is regex so slow? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2013-06-18 20:10 +0200
      Re: Why is regex so slow? Roy Smith <roy@panix.com> - 2013-06-18 12:40 -0700
      Re: Why is regex so slow? André Malo <ndparker@gmail.com> - 2013-06-18 21:59 +0200
        Re: Why is regex so slow? André Malo <ndparker@gmail.com> - 2013-06-18 22:13 +0200
  Re: Why is regex so slow? MRAB <python@mrabarnett.plus.com> - 2013-06-18 18:31 +0100
  Re: Why is regex so slow? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-18 18:34 +0100
    Re: Why is regex so slow? roy@panix.com (Roy Smith) - 2013-06-18 15:21 -0400
      Re: Why is regex so slow? MRAB <python@mrabarnett.plus.com> - 2013-06-18 20:49 +0100
  Re: Why is regex so slow? Rick Johnson <rantingrickjohnson@gmail.com> - 2013-06-18 12:21 -0700
  Re: Why is regex so slow? Antoine Pitrou <solipsis@pitrou.net> - 2013-06-18 20:05 +0000
    Re: Why is regex so slow? Roy Smith <roy@panix.com> - 2013-06-18 13:23 -0700
      Re: Why is regex so slow? Duncan Booth <duncan.booth@invalid.invalid> - 2013-06-19 13:21 +0000
        Re: Why is regex so slow? Roy Smith <roy@panix.com> - 2013-06-19 12:55 -0700
    Re: Why is regex so slow? Grant Edwards <invalid@invalid.invalid> - 2013-06-18 20:30 +0000
      Re: Why is regex so slow? Terry Reedy <tjreedy@udel.edu> - 2013-06-18 17:29 -0400
      Re: Why is regex so slow? Johannes Bauer <dfnsonfsduifb@gmx.de> - 2013-06-19 10:29 +0200
  Re: Why is regex so slow? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-19 01:51 +0000
    Re: Why is regex so slow? Dave Angel <davea@davea.name> - 2013-06-18 22:11 -0400
      Re: Why is regex so slow? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-06-19 03:16 +0000

csiph-web