[Rcpp-devel] Multiplication of ComplexVector?

[Christian Gunning]

I'm using a package generated by Rcpp.package.skeleton.  No C files.
Upon reflection, I'm not entirely sure I have the header right,
though.

///////
// rcpp_operators.h:
///////
#ifndef _Rcwttest_RCPP_OPERATORS_H
#define _Rcwttest_RCPP_OPERATORS_H
#include <Rcpp.h>
RcppExport Rcomplex operator*(const Rcomplex&, const Rcomplex&);
RcppExport Rcomplex operator*(const Rcomplex&, const double&);
#endif

///////
// rcpp_operators.cpp
///////
#include "rcpp_operators.h"
Rcomplex operator*( const Rcomplex& lhs, const double& rhs){
       Rcomplex y ;
       y.r = lhs.r * rhs;
       y.i = lhs.i * rhs ;
       return y ;
}
Rcomplex operator*( const Rcomplex& lhs, const Rcomplex& rhs){
       Rcomplex y ;
       y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
       y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
       return y ;
}


Compiler output (from "R CMD build Rcwttest; R CMD INSTALL Rcwttest;"):

g++ -I/usr/share/R/include
-I"/usr/local/lib/R/site-library/Rcpp/include"   -fpic  -g -O2 -c
rcpp_cwt_thierry.cpp -o rcpp_cwt_thierry.o
In file included from rcpp_cwt_thierry.cpp:2:
rcpp_operators.h:7: error: declaration of C function ‘Rcomplex
operator*(const Rcomplex&, const double&)’ conflicts with
rcpp_operators.h:6: error: previous declaration ‘Rcomplex
operator*(const Rcomplex&, const Rcomplex&)’ here


-xian

On Tue, Aug 17, 2010 at 11:30 PM, Romain Francois
<romain at r-enthusiasts.com> wrote:
> Le 18/08/10 08:19, Romain Francois a écrit :
>>
>> Le 18/08/10 07:44, Christian Gunning a écrit :
>>>
>>> Thanks to all for the helpful suggestions. I was excited to learn
>>> about Armadillo's plans for fft/ifft -- my original interest in Rcpp
>>> was to facilitate the R fft call from C...
>>>
>>> For conceptual simplicity, I'm opting for manually adding an operator*
>>> for now.
>>
>> Note that they will appear in the next version of Rcpp, which is
>> scheduled (loosely) for the end of august.
>>
>>> Benchmarks show a ~10% speedup over sending large vectors (2
>>> million) to R for multiplication.
>>>
>>> One question that I ran into that I don't quite understand -- there
>>> are several permutations of an Rcomplex-returning operator*, depending
>>> upon the type of lhs and rhs (e.g Rcomplex and Rcomplex; Rcomplex and
>>> double; etc.). I admit, the template system is over my head for now,
>>> and this has a low priority for me, but perhaps there's a simple
>>> explanation asides from using separate operator symbols?
>>>
>>> Here are 2 definitions that vary in input type:
>>>
>>> Rcomplex operator*( const Rcomplex& lhs, const Rcomplex& rhs){
>>> Rcomplex y ;
>>> y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
>>> y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
>>> return y ;
>>> }
>>>
>>> Rcomplex operator*( const Rcomplex& lhs, const double& rhs){
>>> Rcomplex y ;
>>> y.r = lhs.r * rhs ;
>>> y.i = lhs.i * rhs ;
>>> return y ;
>>> }
>>>
>>> yielding the following compiler error:
>>>
>>> rcpp_operators.h:7: error: declaration of C function ‘Rcomplex
>>> operator*(const Rcomplex&, const double&)’ conflicts with
>>> rcpp_operators.h:6: error: previous declaration ‘Rcomplex
>>> operator*(const Rcomplex&, const Rcomplex&)’ here
>>>
>>> best,
>>> Christian
>>
>> Do you include this from a .c file or a .cpp file ? C has no concept of
>> overloading.
>>
>> Can you share a small reproducible example that shows the problem.
>>
>> Romain
>
> It seems to work fine for me :
>
> require( inline )
> require( Rcpp )
>
> inc <- '
> Rcomplex operator*( const Rcomplex& lhs, const Rcomplex& rhs){
>        Rcomplex y ;
>        y.r = lhs.r * rhs.r - lhs.i * rhs.i ;
>        y.i = lhs.r * rhs.i + rhs.r * lhs.i ;
>        return y ;
> }
> Rcomplex operator*( const Rcomplex& lhs, const double& rhs){
>       Rcomplex y ;
>       y.r = lhs.r * rhs ;
>       y.i = lhs.i * rhs ;
>       return y ;
> }
>
> '
> fx <- cxxfunction( signature( ), '
> using namespace Rcpp ;
>    Rcomplex x, y ;
>    x.r = 2.0 ; x.i = 2.0 ;
>    y.r = 1.0 ; y.i = 1.0 ;
>
>    Rcomplex z = x * y ;
>    Rcomplex a = x * 3 ;
>    return ComplexVector::create( x, y, z, a ) ;
>
> ', plugin = "Rcpp", includes = inc )
>
>
>
>> fx()
> [1] 2+2i 1+1i 0+4i 6+6i
>
> so I'm staying with my guess that this is a C vs C++ issue.
>
> Romain
>
>
> --
> Romain Francois
> Professional R Enthusiast
> +33(0) 6 28 91 30 30
> http://romainfrancois.blog.free.fr
> |- http://bit.ly/bzoWrs : Rcpp svn revision 2000
> |- http://bit.ly/b8VNE2 : Rcpp at LondonR, oct 5th
> `- http://bit.ly/aAyra4 : highlight 0.2-2
>
>



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