Message-ID: <Pine.LNX.4.44.0305062026470.1186-100000@gannet.stats>
Date: 2003-05-06T19:30:22Z
From: Brian Ripley
Subject: Loops and memory
In-Reply-To: <Law11-F84RGkQ6mBySs00000d8f@hotmail.com>
On Tue, 6 May 2003, R A F wrote:
> I'm afraid that I don't have your new book with Venables handy. So
> would it be fair to assume that there's no real need to avoid loops
> these days?
No, but the issues are different from those in 1996. It is a lot less
common to have to avoid loops, simply because memory can often be
squandered. But vectorizing calculations still pays off, sometimes
handsomely: there is an example in that book of going from several hours
to one second (and it's a real example).
> >From: Prof Brian Ripley <ripley at stats.ox.ac.uk>
> >To: R A F <raf1729 at hotmail.com>
> >CC: r-help at stat.math.ethz.ch
> >Subject: Re: [R] Loops and memory
> >Date: Tue, 6 May 2003 20:03:08 +0100 (BST)
>
> >That was written in 1996, when rich people had 64Mb of RAM and teaching
> >labs often had 4 or 8Mb (and R would not run much of the code in the book
> >and crashed quite often). Take a look at `S Programming' for a less
> >ancient view.
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595