[R-SIG-Mac] FAQ? Mac distributed/multiple processor solutions?

[Ken Beath]

On 06/12/2007, at 9:13 PM, Prof Brian Ripley wrote:

> On Thu, 6 Dec 2007, Ken Beath wrote:
>
>> On 05/12/2007, at 5:57 AM, Thomas Lumley wrote:
>>
>>> On Tue, 4 Dec 2007, Rob Forsyth wrote:
>>>> options here. I am working on an iMac G5 and could access (at  
>>>> home -
>>>> i.e. not on a LAN) another G5 and a G4. I've come across the R/MPI
>>>> package but would appreciate advice as to how easy this is to set  
>>>> up
>>>> (would it actually be simpler to divide the job "manually"?).
>>>
>>> With only three computers it would be easiest to divide the job
>>> manually.
>>>
>>
>> Much easier, and if you have access to a machine with multiple
>> processors, simply duplicate the R process to have the same number as
>> the number of processors, and then run them simultaneously. Not as
>> elegant and maybe not as efficient as other methods, but effective.
>
> But those processes need to do different things (and record the  
> results in
> different files), which is what Thomas means by 'divide the job  
> manually'.
>
> Incidentally, I find it useful to run slightly more R processes than  
> the
> number of processors, to ensure full CPU usage when one of the  
> processes
> is in an I/O wait or hits a swapping trap.  (Provided you have ample  
> RAM
> or you will get additional swapping.)
>
> Even with many processors it may be easisest to do this manually.  Our
> geneticists do simulation-based inference by running separate  
> simulation
> runs on up to 100s of processors simultaneously: the scheduler works
> better with independent jobs.
>

I meant duplicate the R application, using the Finder. I thought it  
was unnecessary to mention that it will require a different set of  
commands to be run in each copy of R.

Ken