Parallelism (was Re: [R] Re: R-1.1.0 is released : GUI)

[Thomas Lumley]

On 17 Jun 2000, Peter Dalgaard BSA wrote:

> There are many levels of parallelism, not all of which are equally
> easy to exploit. At the coarsest level, each machine does essentially
> its own thing in a separate process. This is very easy to implement
> and quite useful for e.g. simulations. For a somewhat more elaborate
> version of this there is the Condor project at Wisconsin which allows
> processes to be moved around between different CPUs - R has been tested
> on this but I don't know how far they've got. 

For Linux there is also MOSIX, which works very nicely for load balancing
on a cluster of PCs.  As most of my computationally intensive work is
simulation or bootstrapping it parallelises very nicely by doing eg 5 lots
of 200 runs rather than one lot of 1000.

> At the finest level there's a potential for very highly optimized
> algorithms for specific purposes like matrix inversion, sorting, and
> differential equation solving. Even though they have been known to be
> theoretically possible for ages, actual implementations seem to be
> slow in coming. 

There are some sparse matrix implementations out there, which may be
linkable to R.  I have used the single-processor version of the Aztec
sparse matrix library with R and I think it would be possible to use the
multi-processor version


	-thomas

Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle

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