Path: csiph.com!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <d@davea.name>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.005
X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'interpreter': 0.04; 'true,': 0.04; 'binary': 0.05; 'float': 0.05; 'removes': 0.05; 'python': 0.09; 'cc:addr:python-list': 0.10; "wouldn't": 0.11; 'subject:python': 0.11; '1:48': 0.16; '3.2.': 0.16; 'ah,': 0.16; 'binary.': 0.16; 'formed,': 0.16; 'later).': 0.16; 'oct': 0.16; 'wrote:': 0.17; 'intel': 0.17; 'import': 0.21; 'cc:2**0': 0.23; 'cc:no real name:2**0': 0.24; 'machine': 0.24; 'tried': 0.25; 'least': 0.25; 'cc:addr:python.org': 0.25; 'header:In-Reply-To:1': 0.25; 'header:User-Agent:1': 0.26; '(which': 0.26; 'am,': 0.27; 'guess': 0.27; 'operations,': 0.27; 'chris': 0.28; 'argue': 0.29; 'decimal': 0.29; 'factor': 0.29; 'class': 0.29; "i'm": 0.29; 'maybe': 0.29; 'function': 0.30; 'point': 0.31; 'anybody': 0.32; 'doubt': 0.33; 'largely': 0.33; 'skip:d 20': 0.34; 'done': 0.34; 'machines': 0.35; 'possible': 0.37; 'being': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'received:192': 0.39; 'received:192.168': 0.40; 'sincerely': 0.60; 'within': 0.64; 'header:Reply-To:1': 0.68; 'received:74.208': 0.71; 'reply-to:no real name:2**0': 0.72; 'subjectcharset:utf-8': 0.72; '100': 0.78; 'subject:get': 0.81; 'copy-paste': 0.84; 'float,': 0.84; 'subject:value': 0.84; 'apparent': 0.91; 'dozen': 0.91; 'angel': 0.93
Date: Mon, 08 Oct 2012 11:13:42 -0400
From: Dave Angel <d@davea.name>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0
MIME-Version: 1.0
To: Chris Angelico <rosuav@gmail.com>
Subject: =?UTF-8?B?UmU6IFRvIGdldCB0aGUgYWNjdXJhdGUgdmFsdWUgb2YgMSAtIDAuOTk=?= =?UTF-8?B?OTk5OTk5OTk5OTk5OSAsaG93IHRvIGltcGxlbWVudCB0aGUgcHl0aG9uIGFsZ28=?= =?UTF-8?B?cml0aG0g77yf?=
References: <91ff9b33-c212-4be0-8ed0-1f6b16f56865@googlegroups.com> <5072E7CC.2070405@davea.name> <CAPTjJmons5fwExNOaug0dNsym2eLe5Pduh6cVqynSAPoSowQdQ@mail.gmail.com>
In-Reply-To: <CAPTjJmons5fwExNOaug0dNsym2eLe5Pduh6cVqynSAPoSowQdQ@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
X-Provags-ID: V02:K0:mFCZu0hzVMeDcLrHVDge+0lmhPMdkHHScwjlSExn3LC GQLICk8aKS4dkZxRUZgWwrDn0VCIYyOjHQY0Z6u3GiM7b1ueDm 2kFRIw32Ct5wPhgZ1ME75kRMYKz3iKzOQrE1TcrjrHNrFpL48+ KU0S7y4xtc7zSyOabXk2Ya4OEcbwQZmTbmv3YmXGcS6Ub/479Q RLrrbvny6KKi7qGrZHnR2CyRA7manroGY7dy8fVydJQ+xngsX9 VQgdtPnciAMdNel4TM3R1l+7jdvGHWXdNqRJ3K/a1Ysc3CJpHM nAdbmZFJQP+Wof+O/LpiwVJAF1ID4FXKfQ2wO+fYE12RSM8MA= =
Cc: python-list@python.org
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
Reply-To: d@davea.name
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.1954.1349709246.27098.python-list@python.org>
Lines: 34
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1349709246 news.xs4all.nl 6870 [2001:888:2000:d::a6]:40497
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:30962

On 10/08/2012 11:00 AM, Chris Angelico wrote:
> On Tue, Oct 9, 2012 at 1:48 AM, Dave Angel <d@davea.name> wrote:
>> import decimal
>> a = decimal.Decimal(4.3)
>> print(a)
>>
>> 5.0999999999999996447286321199499070644378662109375
> Ah, the delights of copy-paste :)
>
>> The Decimal class has the disadvantage that it's tons slower on any modern machine I know of...
> Isn't it true, though, that Python 3.3 has a completely new
> implementation of decimal that largely removes this disadvantage?
>
> ChrisA

I wouldn't know, I'm on 3.2.  However, I sincerely doubt if it's within
a factor of 100 of the speed of the binary float, at least on
pentium-class machines that do binary float in microcode. A dozen years
or so ago, when the IEEE floating point standard was still being formed,
I tried to argue the committee into including decimal in the standard
(which they did much later).  Had it been in the standard then, we MIGHT
have had decimal fp on chip as well as binary.  Then again, the standard
was roughly based on the already-existing Intel 8087, so maybe it was
just hopeless.

I guess it's possible that for some operations, the cost of the
byte-code interpreter and function lookup, etc. might reduce the
apparent penalty.  Has anybody done any timings?


-- 

DaveA