R/CPU problems with openmosix

We've got a problem using R (http://www.r-project.org
<http://www.r-project.org/> ) to do matrix multiplication on our
openmosix cluster.  When we force the R job to run on node #1
(login/head node), it uses ~99% CPU, but if we force it to run on any
other node (5 nodes), the job only uses 60 - 75% of the CPU and so takes
longer to run.  Here is the code we're using to reproduce the problem:

 

n <- 200

for(iter in 1:(10000)){

  M <- diag(seq(0, 1, , n))%*%diag(seq(1, 2, , n))%*%diag(seq(0, 1, ,
n)) }

 

 

The strange thing is that if we set n to 125, it uses ~99% CPU on all
the nodes, but other numbers get different results.  Here is an
approximate chart:

 

#   n   %CPU

 

#  125    99

#  130    60

#  500    75

 

 

Any idea what might be causing this problem?

 

Thanks,

 

Richard