[R-SIG-Mac] Perplexed benchmark result from a new Macbook Pro Core i5

[Stefan Evert]

Just a thought: Wouldn't it make more sense to compare the "elapsed"  
times, which show that both machines are more or less equally fast  
(with a slide edge for the newer i5)?

I suspect that there is a change in the way "user" time is reported,  
which probably adds up running times of four hyperthreads running on  
two cores for the i5 CPU vs. only two threads on two cores for the  
Core 2 Duo.  If I'm not mistaken about the i5 architecture, this is  
not surprising: there are 4 threads, but they have to share 2 cores  
and don't seem to be able to run the FP instructions in parallel on a  
single core; so they're running at half speed only.

Thanks for the benchmark, by the way.  It's good to know I'm not  
missing out on R performance with my good old 2008 MacBook Pro. :-)

Cheers,
Stefan


On 8 May 2010, at 20:53, Gardar Johannesson wrote:

> ###########################################
> ## Results from new macbook pro (Core i5 @ 2.4Ghz)
>
>> set.seed(1)
>> A <- matrix(rnorm(2000*2000),2000,2000)
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  2.500   0.058   0.816
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  2.502   0.050   0.814
>> system.time(solve(B))
>   user  system elapsed
>  7.208   0.265   2.740
>> system.time(solve(B))
>   user  system elapsed
>  7.121   0.264   2.666
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  2.964   0.602   3.528
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  3.040   0.732   3.732
>

> ###################################################
> ## Results from old macbook pro (Core 2 Duo @ 2.2GHz)
>
>> set.seed(1)
>> A <- matrix(rnorm(2000*2000),2000,2000)
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  1.429   0.073   0.800
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  1.429   0.064   0.874
>> system.time(solve(B))
>   user  system elapsed
>  4.532   0.285   2.860
>> system.time(solve(B))
>   user  system elapsed
>  4.521   0.281   2.834
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  3.501   0.764   4.215
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  3.459   0.702   4.113
>> sessionInfo()
> R version 2.11.0 (2010-04-22)
> i386-apple-darwin9.8.0
>
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>>
>
>
> ###################################################
> ## Results from new macbook pro (Core i5 @ 2.4Ghz)
> ## Linking against Goto2 BLAS (vs vecLib)
>
>> set.seed(1)
>> A <- matrix(rnorm(2000*2000),2000,2000)
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  2.348   0.124   0.635
>> system.time(B <- crossprod(A))
>   user  system elapsed
>  2.342   0.110   0.622
>> system.time(solve(B))
>   user  system elapsed
>  6.634   0.327   2.158
>> system.time(solve(B))
>   user  system elapsed
>  6.697   0.348   2.034
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  2.577   0.548   2.885
>> system.time({a <- rep(1.0,100); for(i in 1:1e6) a <- 1.0*a+0.0})
>   user  system elapsed
>  2.411   0.478   2.859