Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!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 0.000
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; '(at': 0.04; 'essentially': 0.04; 'accelerator': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:skip:c 10': 0.09; 'type,': 0.09; 'python': 0.11; 'dict': 0.16; 'elem': 0.16; 'from:addr:behnel.de': 0.16; 'from:addr:stefan_ml': 0.16; 'from:name:stefan behnel': 0.16; 'general.': 0.16; 'iterable:': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:plane.gmane.org': 0.16; 'received:t-ipconnect.de': 0.16; 'self[elem]': 0.16; 'subject:slow': 0.16; 'subtype': 0.16; 'url:file': 0.16; 'bit': 0.19; 'stefan': 0.19; 'seems': 0.21; 'header:User-Agent:1': 0.23; 'looks': 0.24; 'least': 0.26; 'code:': 0.26; 'header:X-Complaints-To:1': 0.27; 'header:In-Reply- To:1': 0.27; 'function': 0.29; 'thus': 0.29; "doesn't": 0.30; 'code': 0.31; '(although': 0.31; 'overhead': 0.31; 'steven': 0.31; 'class': 0.32; 'url:python': 0.33; 'cases': 0.33; 'skip:_ 10': 0.34; 'problem': 0.35; 'possible.': 0.35; 'but': 0.35; 'method': 0.36; 'url:org': 0.36; 'ends': 0.38; 'generic': 0.38; 'to:addr :python-list': 0.38; 'to:addr:python.org': 0.39; 'enough': 0.39; 'received:org': 0.40; 'even': 0.60; 'skip:n 10': 0.64; 'url:c': 0.67; 'benefit': 0.68; 'special': 0.74; 'feet.': 0.84; 'received:87.139': 0.84; 'url:cpython': 0.84
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Stefan Behnel <stefan_ml@behnel.de>
Subject: Re: collections.Counter surprisingly slow
Date: Mon, 29 Jul 2013 13:46:58 +0200
References: <roy-8C60F5.15590428072013@news.panix.com> <51f5843f$0$29971$c3e8da3$5496439d@news.astraweb.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Gmane-NNTP-Posting-Host: p578ba676.dip0.t-ipconnect.de
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7
In-Reply-To: <51f5843f$0$29971$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: <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.5225.1375098437.3114.python-list@python.org>
Lines: 26
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1375098437 news.xs4all.nl 15898 [2001:888:2000:d::a6]:55049
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:51435

Steven D'Aprano, 28.07.2013 22:51:
> Calling Counter ends up calling essentially this code:
> 
> for elem in iterable:
>     self[elem] = self.get(elem, 0) + 1
> 
> (although micro-optimized), where "iterable" is your data (lines). 
> Calling the get method has higher overhead than dict[key], that will also 
> contribute.

It comes with a C accelerator (at least in Py3.4dev), but it seems like
that stumbles a bit over its own feet. The accelerator function special
cases the (exact) dict type, but the Counter class is a subtype of dict and
thus takes the generic path, which makes it benefit a bit less than possible.

Look for _count_elements() in

http://hg.python.org/cpython/file/tip/Modules/_collectionsmodule.c

Nevertheless, even the generic C code path looks fast enough in general. I
think the problem is just that the OP used Python 2.7, which doesn't have
this accelerator function.

Stefan