[R] random number generation issues with r and compiled C code

[Prof Brian D Ripley]

On Fri, 25 Jan 2002, Faheem Mitha wrote:

>
>
> On Thu, 24 Jan 2002, Prof Brian Ripley wrote:
>
> > 3) When using standalone Rmathlib
> >
> >   A little care is needed to use the random-number routines. You will
> >   need to supply the uniform random number generator
> >
> >   double unif_rand(void)
> >
> >   or use the one supplied (and with a shared library or DLL you will have
> >   to use the one supplied, which is the Marsaglia-multicarry with an entry
> >   point
> >
> >   set_seed(unsigned int, unsigned int)
> >
> >   to set its seeds).
> >
> > So, I'm not clear if you have supplied your own or used the one supplied,
> > but if the latter, you need to call set_seed, *but only once*.
>
> Thank you for the reply. I used the one supplied (set_seed). So can I call
> set_seed from the top level of my C code; ie from main(), which then calls
> other functions which call unif_rand() etc?

Yes, you can do it.  What it does is to set internal C variables which
unif_rand() consults.  It's all in .../src/nmath/standalone/sunif.c, and
it is easier to read the code than to try explain it to you in words.

-- 
Brian D. Ripley,                  ripley at 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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._