Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!news.etla.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed2.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 0.002
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'subject:code': 0.07; 'subject:help': 0.08; 'function,': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'throws': 0.09; 'def': 0.12; 'latter,': 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; 'runtime.': 0.16; 'so.': 0.16; 'wrote:': 0.18; 'header:User-Agent:1': 0.23; 'error': 0.23; 'rid': 0.24; 'header:X-Complaints-To:1': 0.27; 'kevin': 0.30; 'skip:( 20': 0.30; 'code': 0.31; 'maybe': 0.34; 'convert': 0.35; 'possible': 0.36; 'should': 0.36; 'form,': 0.38; 'to:addr:python- list': 0.38; 'rather': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'how': 0.40; 'skip:n 10': 0.64; 'subject:Need': 0.64; 'skip:w 30': 0.69; 'matrix.': 0.84
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Peter Otten <__peter__@web.de>
Subject: Re: Need help vectorizing code
Date: Sat, 18 Jan 2014 22:50 +0100
Organization: None
References: <140f8aea-d3c5-4c0d-94f5-6aa064e353d1@googlegroups.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 7Bit
X-Gmane-NNTP-Posting-Host: p5084b942.dip0.t-ipconnect.de
User-Agent: KNode/4.7.3
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: <https://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: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.5691.1390081794.18130.python-list@python.org>
Lines: 37
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1390081794 news.xs4all.nl 2880 [2001:888:2000:d::a6]:46030
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:64261

Kevin K wrote:

> I have some code that I need help vectorizing.
> I want to convert the following to vector form, how can I? I want to get
> rid of the inner loop - apparently, it's possible to do so. X is an NxD
> matrix. y is a 1xD vector.
> 
> def foo(X, y, mylambda, N, D, epsilon):
> ...
>         for j in xrange(D):
>             aj = 0
>             cj = 0
>             for i in xrange(N):
>                 aj += 2 * (X[i,j] ** 2)
>                 cj += 2 * (X[i,j] * (y[i] - w.transpose()*X[i].transpose()
>                 + w[j]*X[i,j]))
> 
> ...
> 
> If I call numpy.vectorize() on the function, it throws an error at
> runtime.

Maybe 

a = (2*X**2).sum(axis=0)
c = no idea.

Judging from the code y should be 1xN rather than 1xD. Also, should

w.transpose()*X[i].transpose()

be a vector or a scalar? If the latter, did you mean

numpy.dot(w, X[i])

?