Re: [R] when can we expect Prof Tierney's compiled R?

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Thu 21 Apr 2005 - 15:28:37 EST

On Wed, 20 Apr 2005, Peter Dalgaard wrote:

> Luke Tierney <luke@stat.uiowa.edu> writes:
>
>> Vectorized operations in R are also as fast as compiled C (because
>> that is what they are :-)). A compiler such as the one I'm working on
>> will be able to make most difference for non-vectorizable or not very
>> vectorizable code. It may also be able to reduce the need for
>> intermediate allocations in vectorizable code, which may have other
>> benefits beyond just speed improvements.
>
> Actually, it has struck me a couple of times that these operations are
> not as fast as they could be, since they are outside the scope of fast
> BLAS routines, but "embarrassingly parallel" code could easily be
> written for the relevant hardware. Even on uniprocessor systems there
> might be speedups that the C compiler cannot find (e.g. because it
> cannot assume that source and destination of the operation are
> distinct).

Enter the 'restrict' keyword of C99, which is used to assure things like that.

Expect to see some performance improvements as we move towards C99 and also supporting the visibility features of gcc4 (and so do the OS's libc and headers).

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Thu Apr 21 15:38:05 2005

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