[R] 64 bit R slower than 32 bit R on Sun Sparc Solaris?

[Prof Brian Ripley]

On Wed, 8 Sep 2004, Jason Liao wrote:

> Thank you very much, Profs. Ripley and Peng! It corrected a big
> misconception in my mind. 
> 
> By the way, does the Sun Forte 7 compiler produce faster R than the GCC
> 3.4.1 compiler (which we use)?

Not in my experience, although libsunperf helps a lot on some problems
(but ATLAS seems competitive).  I mainly use Forte 7 to test the validity 
of source code: gcc is far too generous, especially as is compiles `GNU 
Fortran' not ISO Fortran.

> 
> Jason
> 
> --- Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> 
> > On Tue, 7 Sep 2004, Roger D. Peng wrote:
> > 
> > > Are you using an optimized BLAS for both builds?  That's one
> > > possibility.  Also, 64-bit builds use up more memory initially
> > since the
> > > pointers are bigger.  I've tried both 64-bit and 32-bit builds on
> > > Sparc/Solaris and haven't seen any slowdown.
> > 
> > It uses more memory at all times and so gc() takes longer.  There
> > *is* a
> > slowdown, for example 90 vs 80 secs for a run of R-devel's stats-Ex.R
> > (for
> > either Sun's Forte 7 or gcc 3.4.1 compilers).  But `25-30% slower' is
> > unexpected and needs investigation.
> > 
> > The only difference between 32-bit and 64-bit versions of R on
> > Solaris 
> > will be the size of the pointers and (probably) less efficient PIC
> > code.
> > There is no reason to expect a performance boost with 64-bit
> > applications: 
> > they have to do more work and are only worthwhile if you need the
> > address 
> > space (in memory or also on disc as 64-bit applications use large
> > files 
> > natively).
> > 
> > 
> > > Jason Liao wrote:
> > > 
> > > > Hello, everyone! I guess no one is still using R on Sun Sparc
> > these
> > > > days. But our department has a (pretty new) two-CPU Sun server.
> > We
> > > > recently compiled R as a 64 bit application and expected a
> > performance
> > > > boost. But it runs 25-30% slower than the 32 bit version of R.
> > Anyone
> > > > knows why this is so? Thanks!
> > 
> > -- 
> > 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
> > 
> > 
> 
> 
> =====
> Jason Liao, http://www.geocities.com/jg_liao
> Dept. of Biostatistics, http://www2.umdnj.edu/bmtrxweb
> University of Medicine and Dentistry of New Jersey
> phone 732-235-5429, School of Public Health office
> phone 732-235-8611, Cancer Institute of New Jersey office
> moble phone 908-720-4205
> 
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> 

-- 
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