[R] snow documentation comments

[Ross Boylan]

There are a few points I found unclear or unmentioned in the snow
documentation (mostly I looked at the cluster.html web page).  I thought
I'd mention them here.

What is the start up environment for the children?
--------------------------------------------------
My best guess at the answer is in parentheses
Do they inherit shell variables? (no)
Do they inherit variables set in R or other aspects of the R
environment? (no)
What directory does it start in? (the directory you are running in)
What user are you? (same as original)

I realize some of these answers might depend on the parallelization
layer you are using, or whether you select the homogenous option.

There are also some entertaining pathological cases; for example,
lam/mpi lets you start some of the children as another user.

Number of nodes or number of children?
--------------------------------------
I thought all the counts of nodes (e.g., in makeCluster(5)) were of the
total nodes in the cluster, i.e., children + 1.  However, I did a
makeCluster(2) and I got 2 additional R processes running.  Have I
misunderstood the semantics, or is it essentially an implementation
detail that the master node starts a new R process?

Options
-------
Is the full set of cluster options documented anywhere?

-- 
Ross Boylan                                      wk:  (415) 502-4031
530 Parnassus Avenue (Library) rm 115-4          ross at biostat.ucsf.edu
Dept of Epidemiology and Biostatistics           fax: (415) 476-9856
University of California, San Francisco
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