[Rcpp-devel] bizarre behavior of RcppMatrix

[Yi-Hsin Erica Tsai]

Sorry, I forgot to mention my installation details:

I'm running R version 2.11.0, Rcpp 0.8.0, on Ubuntu Hardy Heron.

Best,
--Erica

On 5/24/2010 8:58 PM, Yi-Hsin Erica Tsai wrote:
> Hi,
>
> I've just started using Rcpp with the hopes of speeding up some R loops
> through replacement with C++ code. I've been struggling with
> understanding the behavior of the NumericMatrix datatype and more
> generally how to pass matrices between R and C++.
>
> I seem to be getting bizarre behavior when I pass default parameters to
> my C++ functions. For example, take this C++ function and the
> corresponding R wrapper function:
>
> ______________________________________
>
> //testRcppMatrix.cpp
>
> #include <Rcpp.h>
>
> RcppExport SEXP plusonediag_RcppMatrix(SEXP matrix)
> {
> Rcpp::NumericMatrix orig(matrix);
> Rcpp::NumericMatrix plus(matrix);
>
> int n = orig.rows();
> int k = orig.cols();
>
> for (int i=0; i<n; i++)
> {
> if(i <= k)
> {
> plus(i,i) = plus(i,i) + 1;
> }
> }
>
> Rcpp::Pairlist res(Rcpp::Named( "original", orig),
> Rcpp::Named( "plus", plus)
> );
>
> return res;
> }
> ______________________________________
>
> #testRcpp.r
>
> plusonediag_RcppMatrix_wrapper <- function(mat=matrix(seq(1,9)^2, ncol=3))
> {
> ## Make the call...
> val <- .Call("plusonediag_RcppMatrix",
> mat)
> return(val)
> }
>
> ______________________________________
>
> If I pass actual values to the plusonediag_RcppMatrix_wrapper, then I
> get correct output; however, if I try to use the default parameter (mat)
> or pass a matrix equal to the default matrix, then the original matrix
> appears to be overwritten. See the session output below.
>
> Anyone have any idea what I'm doing wrong? I'd appreciate any help or
> insight into this problem.
>
> I've attached the test files if that's helpful.
>
> Thanks and best wishes,
> --Erica Tsai
>
>  > # main.r
>  >
>  > library(Rcpp)
> Loading required package: inline
>  > dyn.load("testRcppMatrix.so")
>  > source("testRcppMatrix.r")
>  >
>  > foo <- matrix(1:9, 3, 3)
>  > bar <- foo ^ 2
>  >
>  > plusonediag_RcppMatrix_wrapper #default mat is same as bar
> function(mat=matrix(seq(1,9)^2, ncol=3))
> {
> ## Make the call...
> val <- .Call("plusonediag_RcppMatrix",
> mat)
> return(val)
> }
>  > plusonediag_RcppMatrix_wrapper() #does not produce correct output!!
> $original
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
> $plus
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
>  > plusonediag_RcppMatrix_wrapper(foo) #produces correct output
> $original
> [,1] [,2] [,3]
> [1,] 1 4 7
> [2,] 2 5 8
> [3,] 3 6 9
>
> $plus
> [,1] [,2] [,3]
> [1,] 2 4 7
> [2,] 2 6 8
> [3,] 3 6 10
>
>  > plusonediag_RcppMatrix_wrapper(bar) #does not produce correct output!!
> $original
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
> $plus
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
>  > plusonediag_RcppMatrix_wrapper(matrix((1:9), 3, 3)) #produces correct
> output
> $original
> [,1] [,2] [,3]
> [1,] 1 4 7
> [2,] 2 5 8
> [3,] 3 6 9
>
> $plus
> [,1] [,2] [,3]
> [1,] 2 4 7
> [2,] 2 6 8
> [3,] 3 6 10
>
>  > plusonediag_RcppMatrix_wrapper(matrix((1:9)^2, 3, 3)) #does not
> produce correct output!!
> $original
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
> $plus
> [,1] [,2] [,3]
> [1,] 2 16 49
> [2,] 4 26 64
> [3,] 9 36 82
>
>  >
>
>
>
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