Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail Return-Path: 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; 'argument': 0.04; 'subject:Python': 0.05; 'case.': 0.05; 'cpython': 0.05; 'objects,': 0.07; 'repeated': 0.07; 'python': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'runtime': 0.09; 'tuple': 0.09; 'cases': 0.15; 'ecosystem.': 0.16; 'from:addr:behnel.de': 0.16; 'from:addr:stefan_ml': 0.16; 'from:name:stefan behnel': 0.16; 'iteration': 0.16; 'language)': 0.16; 'message-id:@dough.gmane.org': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'stefan': 0.17; '(or': 0.18; 'code.': 0.20; 'subject:skip:i 10': 0.22; 'paul': 0.24; 'header:In-Reply-To:1': 0.25; 'header:User-Agent:1': 0.26; 'common': 0.26; 'implemented': 0.27; "doesn't": 0.28; 'header:X -Complaints-To:1': 0.28; "d'aprano": 0.29; 'loop,': 0.29; 'signatures': 0.29; 'steven': 0.29; 'writes:': 0.29; 'case,': 0.29; 'saves': 0.30; 'function': 0.30; 'compatible': 0.30; 'code': 0.31; 'file': 0.32; 'quickly': 0.32; 'received:84': 0.32; 'apply,': 0.33; 'function.': 0.33; 'turns': 0.33; 'problem': 0.33; 'to:addr:python-list': 0.33; "can't": 0.34; 'faster': 0.35; 'something': 0.35; 'there': 0.35; 'add': 0.36; 'received:org': 0.36; 'but': 0.36; 'expensive': 0.36; 'optimization': 0.37; 'does': 0.37; 'uses': 0.37; 'being': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'things': 0.38; 'performance': 0.39; 'to:addr:python.org': 0.39; 'called': 0.39; 'where': 0.40; 'subject:-': 0.40; 'header:Received:5': 0.40; 'most': 0.61; 'back': 0.62; 'export': 0.62; 'worth': 0.63; 'offer': 0.65; 'fact,': 0.69; 'unusual': 0.71; 'average.': 0.84; 'exercised': 0.84; 'packing': 0.84; 'received:arcor-ip.net': 0.84; 'received:pools.arcor-ip.net': 0.84; 'ridiculously': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Stefan Behnel Subject: Re: On-topic: alternate Python implementations Date: Sun, 05 Aug 2012 07:37:48 +0200 References: <501cbdf8$0$29978$c3e8da3$5496439d@news.astraweb.com> <501cff63$0$29978$c3e8da3$5496439d@news.astraweb.com> <7x1ujmabs9.fsf@ruckus.brouhaha.com> <501dc461$0$29978$c3e8da3$5496439d@news.astraweb.com> <7x1ujm9kyu.fsf@ruckus.brouhaha.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: dslb-084-056-051-236.pools.arcor-ip.net User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0 In-Reply-To: <7x1ujm9kyu.fsf@ruckus.brouhaha.com> X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 29 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1344145080 news.xs4all.nl 6966 [2001:888:2000:d::a6]:60904 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:26525 Paul Rubin, 05.08.2012 03:38: > Steven D'Aprano writes: >> Runtime optimizations that target the common case, but fall back to >> unoptimized code in the rare cases that the optimization doesn't apply, >> offer the opportunity of big speedups for most code at the cost of >> trivial slowdowns when you do something unusual. > > The problem is you can't always tell if the unusual case is being > exercised without an expensive dynamic check, which in some cases must > be repeated in every iteration of a critical inner loop, even though it > turns out that the program never actually uses the unusual case. Cython does a lot of optimistic optimisations. That's where a large part of that huge C file comes from that Cython generates from even simple Python code. For example, in CPython, C function calls are so ridiculously faster than Python function calls that it's worth some effort if it saves you from packing an argument tuple to call into a Python function. In fact, we've been thinking about ways to export C signatures from Python function objects, so that code implemented in C (or a C compatible language) can be called directly from other code implemented in C. That's very common in the CPython ecosystem. There are a lot of simple things that quickly add up into a much better performance on average. Stefan