[Rcpp-devel] Multiplication of ComplexVector?
Christian Gunning
xian at unm.edu
Wed Aug 18 09:12:25 CEST 2010
Got it, thanks!
On Wed, Aug 18, 2010 at 12:10 AM, Romain Francois
<romain at r-enthusiasts.com> wrote:
> Yep, that is because of RcppExport. You only use RcppExport when you call
> the function from .Call in R.
>
> RcppExport is an alias to extern "C" so it essentially voids the C++-ness of
> the function it is applied to.
>
> Romain
>
> Le 18/08/10 09:05, Christian Gunning a écrit :
>>
>> 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
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>
>
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