From ripley at stats.ox.ac.uk  Tue Mar  5 07:11:53 2013
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Tue, 05 Mar 2013 06:11:53 +0000
Subject: [Rd] crossprod(): g77 versus gfortran
In-Reply-To: <51354E30.7090802@gmail.com>
References: <51354E30.7090802@gmail.com>
Message-ID: <51358CA9.4030004@stats.ox.ac.uk>

On 05/03/2013 01:45, Benjamin Tyner wrote:
> Hi
>
> I've got two builds of R, one using g77 (version 3.4.6) and the other
> using gfortran (version 4.1.2). The two builds are otherwise identical
> as far as I can tell. The one which used g77 performs crossprod()s
> roughly twice as fast as the gfortran one. I'm wondering if this rings a
> bell with anyone, and if so, are you aware of any configure settings
> which will improve the performance when using gfortran. This is on RHEL 5.

Note that recent versions of R do not build with g77, and have 
performance improvements in linear algebra.  So please follow the 
posting guide and give up the 'at a minimum' information requested and a 
reproducible example.

Also, check what BLAS is in use: an optimized BLAS can make a lot of 
difference on such simple operations.


-- 
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



[Rd] crossprod(): g77 versus gfortran
Prof Brian Ripley