[Rd] RNGkind() state (PR#12567)

[Ray.Brownrigg at mcs.vuw.ac.nz]

I sent this to R-devel early last month, but have received no response, so I guess it 
really is a bug.

This looks like a bug to me, and is a bit hard to describe, but easy to reproduce.  
Basically, if RNGkind is saved as something other than the default, and if the first 
operation in a session is a set.seed(), the default is reverted to.  Reproduce by:

cafe-rozo>  R --vanilla

R version 2.7.1 (2008-06-23)
Copyright (C) 2008 The R Foundation for Statistical Computing
ISBN 3-900051-07-0

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> sessionInfo()
R version 2.7.1 (2008-06-23)
i386--netbsdelf

locale:
C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base
> set.seed(1); runif(1)         # check the default
[1] 0.2655087
> RNGkind("Mar")
> RNGkind()
[1] "Marsaglia-Multicarry" "Inversion"
> set.seed(1); runif(1)         # now check again
[1] 0.006153224
> set.seed(1)                   # save seed and RNGkind
> q("yes")
cafe-rozo>  R

R version 2.7.1 (2008-06-23)
: etc
[Previously saved workspace restored]

> runif(1)              # with a saved seed, Marsaglia-Multicarry is used
[1] 0.006153224
> set.seed(1); runif(1)
[1] 0.006153224
> q()
Save workspace image? [y/n/c]: n
cafe-rozo> 

R version 2.7.1 (2008-06-23)
: etc
[Previously saved workspace restored]

> set.seed(1); runif(1)         # saved RNGkind is ignored ...
[1] 0.2655087
> RNGkind()             # and overridden ...
[1] "Mersenne-Twister" "Inversion"
> q("no")
cafe-rozo>  R

R version 2.7.1 (2008-06-23)
: etc
[Previously saved workspace restored]

> RNGkind()             # and wrongly reported!
[1] "Mersenne-Twister" "Inversion"
> runif(1)                      # Note this is actually using Marsaglia-Multicarry
[1] 0.006153224
>

Ray Brownrigg
Mathematics, Statistics and Computer Science
Victoria University of Wellington
Wellington, NZ