[R] Syntax for Rmpi cf multicore

[Patrick Connolly]

I'm aiming to compare the workings of Rmpi and multicore on a duel
processor quad core machine with 64 bit R-2.11.1 Kubuntu 10.4.


It's impossible for me to get a small reproducable code segment to
show what I mean, but if I show what works for mclapply, I'd hope it's
possible to be shown what would be the equivalent way with mpi.apply.

The function lr.gbm has variables trees, folds and minob which I use
with mclapply like this:

 out <- mclapply(subsets, lr.gbm, mc.cores = 6, trees=trees, folds=folds,
                  minob=minob)
    
subsets is simply a vector that looks like this:

[1] "COB_2" "CNJ_2" "COB_3" "CNJ_3" "COB_4" "CNJ_4"

and that works more or less fine to produce a list of length 6 which
I've named with the elements of the subsets vector.

  names(out) <- subsets


Now, when I use mpi.apply, I make the trees, folds and minob available
to all slaves thus:

  mpi.spawn.Rslaves(nslaves=6)
  mpi.bcast.Robj2slave(trees)
  mpi.bcast.Robj2slave(folds)
  mpi.bcast.Robj2slave(minob)

but, I can't work out what sort of 'array' is required for the first
argument to mpi.apply.

  out.mpi <- mpi.apply(subsets.l, lr.gbm)

What should subsets.l look like?  I tried a list of length 6 with
elements the same as those in 'subsets', but evidently, something more
array-like is required, but I'm out of ideas.

TIA


-- 
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.   
   ___    Patrick Connolly   
 {~._.~}                   Great minds discuss ideas    
 _( Y )_  	         Average minds discuss events 
(:_~*~_:)                  Small minds discuss people  
 (_)-(_)  	                      ..... Eleanor Roosevelt
	  
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