I started to look at ways to improve times of certain very parallel tasks and
thought that foreach should be a valid candidate to do the job.
So, i opened foreach tutorial by Steve Weston and started timing examples from
it. First example from tutorial is
>system.time(for(i in 1:100000) sqrt(i))
user system elapsed
0.06 0.00 0.06
> system.time(foreach(i=1:100000) %do% sqrt(i))
user system elapsed
102.37 0.21 103.38
Hmm, 1700 time slower?
second example is
> system.time(x <- exp(1:1000000))
user system elapsed
0.34 0.03 0.42
>system.time(x <- foreach(i=1:1000000, .combine='c') %do% exp(i))
I stopped it at 958 seconds, didn't have enough patience -- it basically seems
that foreach slows down this one down naive by more than 2000 times. I must
be doing something very wrong. Am i supposed to set some environment variables
before it works properly? I am running 64bit R on win7 dual core 2.27GHZ CPUs
and 4GB memory laptop.
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