From kingaa at umich.edu  Fri Jan 25 15:10:32 2013
From: kingaa at umich.edu (Aaron King)
Date: Fri, 25 Jan 2013 09:10:32 -0500
Subject: [Rd] maintaining multiple R versions
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	<51000A7A.9030106@gmail.com>
Message-ID: <20130125140948.GA4664@betula>

I agree, environment modules really come into their own when you need to switch back and forth between different versions, as I do when testing my packages.  Since environment modules are used on the cluster I work on, it's actually easier for me to use them on my local machines than to change working styles according to which machine I'm on.

To answer your question, yes, if your OS upgrade doesn't wipe out the needed system libraries, you can continue to use older versions of R.  As to whether a library compiled under one (old) version of gcc will work with any given (newer) version of the system libraries, that will depend on the changes made to gcc, and all of this is resolved by the dynamic linker at runtime.  I don't believe there is any guarantee that gcc's libraries will be fully backward compatible.  At any rate, environment modules only manipulates the user's environment and has no control over what is installed on the system.  Hope this helps. 

On Wed, Jan 23, 2013 at 11:06:18AM -0500, Paul Gilbert wrote:
> For the problem I had in mind, changing a couple of environment
> variables does not seem like more work than this,  but it may solve
> a bigger problem than the one I was thinking about. If I understand
> correctly, you can use this to switch among versions of R, similar
> to what I am doing and still with versions in different directories
> found by a PATH setting. But, in addition, it is also possible that
> the R versions were compiled with different gcc and other tools, as
> long as those are still installed on the system.  Does it also work
> if you upgrade the OS and have newer versions of system libraries,
> etc, or do you then need to recompile the R versions?

-- 
Aaron A. King, Ph.D.
Ecology & Evolutionary Biology
Mathematics
Center for the Study of Complex Systems
University of Michigan
GPG Public Key: 0x15780975



[Rd] maintaining multiple R versions
Aaron King