I think you want to move the RNGScope declaration before the calls to
rcauchy and runif.
On Tue, Aug 14, 2012 at 9:17 AM, Rodney Sparapani <rspar...@mcw.edu> wrote:
> This is my first post so please be gentle ;o) I have been through
> all of the docs that I can find (but I haven't looked at the source
> code directly). Here is the behavior that I see:
>
>> require(inline)
> Loading required package: inline
>> source("helper.R")
>> source("corrMH.R")
>>
>> set.seed(66)
>>
>> for(i in 1:3) print(corrMH(0.2, 0.5, 100, 0))
> [1] -0.07071726
> [1] -8.085111
> [1] -4.004675
>>
>> corrMH.Rcpp <- cxxfunction(
> + signature(a="numeric", b="numeric", N="numeric", x="numeric"),
> + body=cat.file("corrMH.Rcpp.cpp"), plugin="Rcpp")
>>
>> set.seed(66)
>>
>> for(i in 1:3) print(corrMH.Rcpp(0.2, 0.5, 100, 0))
> [1] -0.07071726
> [1] -0.07071726
> [1] -0.07071726
>
> Notice that the Rcpp version of the function returns the same value
> each time (only 3 shown, but this is true no matter how many times
> that you do it). I guess this is because we follow the RNGScope state
> of the RNG, but we don't update it. However, updating is really needed
> in this case. I hope I am making this clear. Please let me know if
> you have any ideas. Thanks
>
> Attachments seem to be allowed so I'm including my code...
>
> Red Hat Enterprise Linux Server release 6.2 (Santiago)
> g++ (GCC) 4.4.6 20110731 (Red Hat 4.4.6-3)
> R version 2.14.2 (2012-02-29)
>
>> installed.packages()["Rcpp", ]
> Package LibPath
> "Rcpp" "/opt/local/lib64/R/library"
> Version Priority
> "0.9.10" NA
> Depends Imports
> "R (>= 2.12.0), methods" NA
> LinkingTo Suggests
> NA "RUnit, inline, rbenchmark"
> Enhances OS_type
> NA NA
> License Built
> "GPL (>= 2)" "2.14.2"
> --
> Rodney Sparapani, PhD Center for Patient Care and Outcomes Research
> Sr. Biostatistician http://www.mcw.edu/pcor
> 4 wheels good, 2 wheels better! Medical College of Wisconsin (MCW)
> WWLD?: What Would Lombardi Do? Milwaukee, WI, USA
>
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