R help - Mar 2004 - snow documentation comments

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
San Francisco, CA 94143-0840                     hm:  (415) 550-1062

On Tue, 23 Mar 2004, Ross Boylan wrote:
> 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.
They do
> 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?
makeCluster(2) creates a cluster of two processes that the master
process uses.  So there are a total of three processes.

luke

-- 
Luke Tierney
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
   Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu