[R] snow apparently using only one CPU (on Mac OS X)

[Santiago Beguería Portugués]

Hi,

I am trying to optimize a complex model calibration using a genetic algorithm. I choose rgenoud package because it allows for easy parallelization through snow package. I am on a Mac Pro with 2 x 2.66 GHz 6-Core Intel Xeon machine, i.e. I have 12 CPUs available. 

So I set the cluster options as:

setDefaultClusterOptions(rshcmd='echo ', user='> /dev/null', master='localhost')

then I start a SOCK type cluster with:

cl <- makeCluster(rep(';',12), type='SOCK')

and then I use:

gnoud(..., cluster=cl)

Then when I check the activity of the CPUs I realize that 12 processes have already started, but the CPU load of each process is extremely low (<4% most of the time). If I use other cluster configurations (i.e., a different number of CPUs) the CPU load per process increases inversely proportional to the number of CPUs. I believe that snow is only using one CPU and sharing the computing time within all the processes. Does anyone have the same experience with snow?

Cheers,

	Santiago Beguería