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

[Liaw, Andy]

I'm not familiar with Solaris, so take this with appropriate dose of NaCl...

For the 64-bit build, why not have the -O2 for gcc, since you have it for
g77 and g++?  If you just run vanilla configure for the 32-bit build, I
believe it uses -O2 for all three compilers by default.  If that's the
difference, perhaps it's sufficient to explain the performance difference.

The other thing is that solve(), and to some extent lm(), can benefit from
an optimized BLAS.  You might want to check if the two builds are using
equivalent BLAS.

Andy

> From: 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(50
> 0*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(50
> 0*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?
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 
> 
>