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

[Prof Brian Ripley]

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