[Rcpp-devel] Problem passing Armadillo objects back to R

[Romain Francois]

Good news. I can reproduce it.
Bas news. This is likely a PROTECT problem with the Rcpp::List constructor.

Wearing my bugbuster costume, and getting ready for a fight.

Romain

Le 07/03/11 23:03, "Günter J. Hitsch" a écrit :
>
> I'm new to Rcpp and RcppArmadillo---so far I like it a lot! Thanks to
> the developers for their good work.
>
> I run into a peculiar kind of problem when I try to pass a "large"
> Armadillo object back to R. Here's some code to replicate the problem in
> stylized form:
>
>
> extern "C" SEXP testFun(SEXP L_)
> {
> const long L = Rcpp::as<long>(L_);
> arma::mat X(L,1);
> arma::mat Y(L,1);
> X.fill(1);
> Y.fill(2);
> return Rcpp::List::create(
> Rcpp::Named("X") = Rcpp::wrap(X),
> Rcpp::Named("Y") = Rcpp::wrap(Y)
> );
> }
>
>
> I compile (both using g++ and the Intel Compiler --- choice of compiler
> makes no difference) and then call from R:
>
>
> L = 1000000
> ret = .Call("testFun", as.integer(L))
> print(ret$X[1:5,])
> print(ret$Y[1:5,])
>
>
> Here's what I often get as output:
>
> [1] 1 1 1 1 1
> [1] 1 1 1 1 1
>
> However, the second rows should be all 2's!
>
> When I try to pass smaller matrices, for example by setting L=100000,
> the problem goes away:
>
> [1] 1 1 1 1 1
> [1] 2 2 2 2 2
>
>
> Also, the problem does not arise when I create and pass pack objects of
> type Rcpp::NumericMatrix; so far I've see the problem only with
> Armadillo objects. I've encountered this on two Macs running OS X
> 10.6.6, R 2.12.2, and I'm using the latest versions of Rcpp and
> RcppArmadillo.
>
> Help on this matter is appreciated!
>
> Günter
>
>
>
> _______________________________________________
> Rcpp-devel mailing list
> Rcpp-devel at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel


-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
http://romain-francois.com
|- http://bit.ly/fhqbRC : Rcpp workshop in Chicago on April 28th
|- http://bit.ly/dFyZGB : Hydraulique au Montpellier Comedie Club
`- http://bit.ly/eVXit9 : Eponyme : 40 minutes stand up