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

Groups > comp.lang.python > #49983

Re: How to make this faster

Path csiph.com!usenet.pasdenom.info!news.albasani.net!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path <oscar.j.benjamin@gmail.com>
X-Original-To python-list@python.org
Delivered-To python-list@mail.python.org
X-Spam-Status OK 0.008
X-Spam-Evidence '*H*': 0.98; '*S*': 0.00; 'algorithm': 0.04; 'column': 0.07; 'grid': 0.09; 'subject:How': 0.10; 'cc:addr :python-list': 0.11; 'python': 0.11; 'dict': 0.16; 'dictionaries': 0.16; 'exists)': 0.16; 'iterating': 0.16; 'numpy': 0.16; 'subject:make': 0.16; 'wrote:': 0.18; 'bit': 0.19; 'meant': 0.20; 'solution.': 0.20; 'cc:addr:python.org': 0.22; 'switched': 0.24; 'looks': 0.24; 'cc:2**0': 0.24; 'cc:no real name:2**0': 0.24; 'header:In-Reply-To:1': 0.27; 'tried': 0.27; 'array': 0.29; 'message-id:@mail.gmail.com': 0.30; 'easier': 0.31; 'keys': 0.31; 'lists': 0.32; 'stuff': 0.32; 'could': 0.34; 'but': 0.35; 'received:google.com': 0.35; 'version': 0.36; 'entry': 0.36; 'seconds': 0.37; 'implement': 0.38; 'even': 0.60; 'kind': 0.63; 'july': 0.63; 'improvement.': 0.68; 'subject:this': 0.83; 'occupied': 0.84; 'oscar': 0.84; '2013': 0.98
DKIM-Signature v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type; bh=vuuXBSI9Vym34ctCsaChjxNaKY473cgxsKCHcgXuyio=; b=X/6phZN5wBp0H2EvreQvR8TB+aiZg2abCGxddLdIXxtfIX+J7hyRYqQI7xzzfNL0ue 81Wo3QCpK8ssGQr3Yx8TmIOn+sKnjsV+fgeg1K+LdYPytEM/kpx7t3ueWtFuuub7B4EO IjR4oE1VrK0x1Js3QDN6s7CP5h/M+ZbnV65krZ636/jIcw1xxCslczgZR3IPEA+H2rJx uv1oFOGmgT1DjY7EtIMHA9QRRDEC0BZe/09iOVes5rjCZzIbig/bbOVNB2MK/k+r7jxI no7Ys/UqBslvR9DnGkisZgfdCg6aTITaaDe2oiL7pgMR28t2/3syOz5s6/bjaNzurpce ozYg==
X-Received by 10.220.191.5 with SMTP id dk5mr6786284vcb.47.1373031704661; Fri, 05 Jul 2013 06:41:44 -0700 (PDT)
MIME-Version 1.0
In-Reply-To <b3nmtfFojnkU3@mid.dfncis.de>
References <b3ne2rFojnkU1@mid.dfncis.de> <b3nmtfFojnkU3@mid.dfncis.de>
From Oscar Benjamin <oscar.j.benjamin@gmail.com>
Date Fri, 5 Jul 2013 14:41:23 +0100
Subject Re: How to make this faster
To Helmut Jarausch <jarausch@igpm.rwth-aachen.de>
Content-Type text/plain; charset=ISO-8859-1
Cc python-list@python.org
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 <http://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 <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups comp.lang.python
Message-ID <mailman.4296.1373031707.3114.python-list@python.org> (permalink)
Lines 26
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1373031707 news.xs4all.nl 15970 [2001:888:2000:d::a6]:48849
X-Complaints-To abuse@xs4all.nl
Xref csiph.com comp.lang.python:49983

Show key headers only | View raw

On 5 July 2013 11:53, Helmut Jarausch <jarausch@igpm.rwth-aachen.de> wrote:
> I even tried to use dictionaries instead of Numpy arrays. This version is a bit
> slower then the lists of lists version (7.2 seconds instead of 6 second) but still
> much faster than the Numpy array solution.

When you switched to dictionaries did you take advantage of the
sparseness by iterating over dictionary keys instead of indices? This
is the kind of thing that I meant when I said that in Python it's
often easier to implement a better algorithm than in C. What I mean is
that if Grid is a dict so that Grid[(r, c)] is the entry at row r and
column c (if it exists) then you can change a loop like:

    for r in range(9):
        for c in range(9):
            if Grid[r, c] > 0: continue
            # do stuff

so that it looks like:

    for r, c in Grid:
        # do stuff

If the grid is sparsely occupied then this could be a significant improvement.


Oscar

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

Thread

How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 08:22 +0000
  Re: How to make this faster Fábio Santos <fabiosantosart@gmail.com> - 2013-07-05 10:38 +0100
  Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 10:07 +0000
  Re: How to make this faster Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-07-05 11:13 +0100
  Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 10:53 +0000
    Re: How to make this faster Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-05 12:02 +0000
    Re: How to make this faster Fábio Santos <fabiosantosart@gmail.com> - 2013-07-05 13:44 +0100
    Re: How to make this faster Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-07-05 14:41 +0100
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 14:28 +0000
      Re: How to make this faster Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-07-05 15:45 +0100
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 14:48 +0000
      Re: How to make this faster Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-07-05 16:26 +0100
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 14:54 +0000
      Re: How to make this faster Fábio Santos <fabiosantosart@gmail.com> - 2013-07-05 16:18 +0100
      Re: How to make this faster Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-05 16:24 +0000
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 15:17 +0000
      Re: How to make this faster Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-07-05 16:38 +0100
      Re: How to make this faster MRAB <python@mrabarnett.plus.com> - 2013-07-05 17:25 +0100
      Re: How to make this faster Joshua Landau <joshua.landau.ws@gmail.com> - 2013-07-06 02:45 +0100
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 15:47 +0000
      Re: How to make this faster Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-05 16:52 +0000
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 16:07 +0000
      Re: How to make this faster Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-05 16:50 +0000
        Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 18:39 +0000
          Re: How to make this faster Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-06 03:05 +0000
          Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-06 07:25 +0000
    Re: How to make this faster Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-07-05 18:42 +0000

csiph-web