[R-sig-hpc] How to check if %dopar% really run parallel?

[Mario Valle]

Is there any way to check that %dopar% really runs parallel?
The following code (on a dual core laptop running windows+R 2.11.0pat 
and on Linux+R2.11.0) runs %dopar% more slowly than the same %do% code.
BTW, if you see any obvious mistake in the code...
Thanks!
		mario


library(doSNOW)
library(foreach)

fun <- function() for(q in 1:1000000) sqrt(3)

system.time(times(10000) %do% fun, gcFirst = TRUE)
#   user  system elapsed
#   5.74    0.01    6.24

cl <- makeCluster(2, type = "SOCK")
registerDoSNOW(cl)

system.time(times(10000) %dopar% fun, gcFirst = TRUE)
#   user  system elapsed
#   7.89    0.19    9.01

stopCluster(cl)

-- 
Ing. Mario Valle
Data Analysis and Visualization Group            | 
http://www.cscs.ch/~mvalle
Swiss National Supercomputing Centre (CSCS)      | Tel:  +41 (91) 610.82.60
v. Cantonale Galleria 2, 6928 Manno, Switzerland | Fax:  +41 (91) 610.82.82