[R] Performance difference between 32-bit build and 64-bit build on Solaris 8

[Scott Gilpin]

Hi everyone -

I'm seeing a 32-bit build perform significantly faster (up to 3x) than
a 64 bit build on Solaris 8.  I'm running R version 2.1.0.  Here are
some of my system details, and some resulting timings:

>uname -a
SunOS lonetree 5.8 Generic_117350-16 sun4u sparc SUNW,Sun-Fire-V440

lonetree /home/sgilpin >gcc -v
Reading specs from /usr/local/lib/gcc/sparc-sun-solaris2.8/3.4.2/specs
Configured with: ../configure --with-as=/usr/ccs/bin/as
--with-ld=/usr/ccs/bin/ld --disable-nls
Thread model: posix
gcc version 3.4.2

I built the 32 bit version of R with no changes to config.site.  I
built the 64 bit version with the following in config.site:

CC="gcc -m64"
FFLAGS="-m64 -g -02"
LDFLAGS="-L/usr/local/lib/sparcv9 -L/usr/local/lib"
CXXFLAGS="-m64 -g -02"

neither build uses a BLAS.  Both builds are installed on the same
machine, and the same disk.  The machine has virtually no load; R is
one of the only processes running during these timings:

First comparison:  solve on a large matrix

>echo 'set.seed(1);M<-matrix(rnorm(9e6),3e3);system.time(solve(M))' |
/disk/loneres01/R-2.1.0-32bit/bin/R -q --vanilla
> set.seed(1);M<-matrix(rnorm(9e6),3e3);system.time(solve(M))
[1] 713.45   0.38 713.93   0.00   0.00
> 

>echo 'set.seed(1);M<-matrix(rnorm(9e6),3e3);system.time(solve(M))' |
/disk/loneres01/R-2.1.0-64bit/bin/R -q --vanilla
> set.seed(1);M<-matrix(rnorm(9e6),3e3);system.time(solve(M))
[1] 2277.05    0.31 2278.38    0.00    0.00
> 

Second comparison:  linear regression

lonetree /home/sgilpin/R >echo 'set.seed(1);
y<-matrix(rnorm(10000*500),500);
x<-matrix(runif(500*100),500);
system.time(fit<-lm(y~x))' | /disk/loneres01/R-2.1.0-32bit/bin/R -q --vanilla  
> set.seed(1);y<-matrix(rnorm(10000*500),500);x<-matrix(runif(500*100),500);system.time(fit<-lm(y~x))
[1] 23.34  0.80 24.17  0.00  0.00
> 

lonetree /home/sgilpin/R >echo 'set.seed(1);
y<-matrix(rnorm(10000*500),500);
x<-matrix(runif(500*100),500);
system.time(fit<-lm(y~x))' | /disk/loneres01/R-2.1.0-64bit/bin/R -q --vanilla 
> set.seed(1);y<-matrix(rnorm(10000*500),500);x<-matrix(runif(500*100),500);system.time(fit<-lm(y~x))
[1] 55.34  0.70 56.21  0.00  0.00
> 

Final comparison:  stats-Ex.R (from R-devel)
lonetree /home/sgilpin/R >time /disk/loneres01/R-2.1.0-32bit/bin/R -q
--vanilla CMD BATCH stats-Ex.R

real    1m4.042s
user    0m47.400s
sys     0m10.390s
lonetree /home/sgilpin/R >time /disk/loneres01/R-2.1.0-64bit/bin/R -q
--vanilla CMD BATCH stats-Ex.R

real    1m20.017s
user    1m3.590s
sys     0m10.130s

I've seen Prof. Ripley and others comment that a 64 bit build will be
a little slower because the pointers are larger, and gc() will take
longer, but these timings seem out of this range.

Any thoughts?