[Rcpp-devel] RcppMAtrix<complex> ?
Romain Francois
romain at r-enthusiasts.com
Mon Apr 26 10:09:50 CEST 2010
And now, with the new macros (see the thread "[Rcpp-devel] any
preprocessor expert around ?" ), one can write the function as:
#include <RcppArmadillo.h>
using namespace Rcpp ;
RCPP_FUNCTION_2( arma::mat, add_mat,
arma::mat y, arma::mat x ){
arma::mat result = x+y;
return result ;
}
although in this case x and y would be copies of the R data, so it would
be less efficient than your code.
Romain
Le 23/04/10 19:55, Davor Cubranic a écrit :
>
> Baptiste,
>
> Do have a look at RcppArmadillo, it makes matrix code very easy to write
> (and read!). For example, this is a function callable from R to add two
> matrices:
>
> #include<RcppArmadillo.h>
>
> using namespace Rcpp;
>
> RcppExport SEXP add_mat(SEXP y_in,
> SEXP x_in) {
> NumericMatrix y_r(y_in);
> arma::mat y(y_r.begin(), y_r.nrow, y_r.ncol(), false);
>
> NumericMatrix x_r(x_in);
> arma::mat x(x_r.begin(), x_r.nrow(), x_r.ncol(), false);
>
> arma::mat result = x+y;
> return wrap(result);
> }
>
> In this case, the matrices are real, not complex. but I believe simply
> replacing 'arma::mat' with 'arma::cx_mat' and 'NumericMatrix' with
> 'ComplexMatrix' will work for the complex case.
>
> Davor
>
>
> On April 22, 2010 01:22:58 pm baptiste auguie wrote:
>> OK, thanks for the information. I guess I was lead to believe that
>> such operations were of common use because I worked previously with
>> colleagues who had defined their own C++ complex class (and I'm
>> guessing it was precisely for this purpose of operator overloading).
>> Sadly the code was not open source. I'll look into armadillo,
>> hopefully it provides an alternative. I might also need to rethink
>> what portion of the code I should really be porting out of R; this
>> function was clearly the bottleneck of my code but it looks like it
>> will be painful to write it in a lower-level language.
>>
>> Thanks,
>>
>> baptiste
>>
>> On 22 April 2010 18:42, Romain Francois<romain at r-enthusiasts.com>
> wrote:
>>> Le 22/04/10 18:19, baptiste auguie a écrit :
>>>> Thanks for the example, it is useful indeed. However, I am having
>>>> difficulties with operations involving whole matrices, rather than
>>>> matrix elements.
>>>
>>> We don't currently have those.
>>>
>>>> Again I must warn that I don't know C++ ; but the
>>>> addition of two matrices does not seem to work out-of-the-box, as
>>>> well as more complicated functions. The dispatch of these
>>>> functions might not exist for the complex matrix class, or maybe
>>>> it is not implemented in Rcpp?
>>>>
>>>> The operations I would need to perform with complex matrices are,
>>>>
>>>> +, -, *, transpose,
>>>> as well as operations on 1-column and one-row matrices (==
>>>> vectors?) such as exp().
>>>
>>> Those are things you'd typically do in R, not in C/C++
>>>
>>>> Working component by component is not a very attractive option
>>>
>>> That is what you usually do in a C/C++ world
>>>
>>>> so I'm
>>>> hoping there is an easy way to define operations between matrices,
>>>> matrices and vectors, and matrices and scalars.
>>>
>>> One thing you can do perhaps is look into armadillo, which we wrap
>>> nicely with the RcppArmadillo package. and thanks to Doug, the
>>> wrapping is even nicer now since armadillo is packed up inside
>>> RcppArmadillo (but this version is not released yet).
>>>
>>> We will not implement these operators soon because it is very easy
>>> to not do it right. armadillo does it nicely.
>>>
>>>> Thanks,
>>>>
>>>> baptiste
>>>>
>>>> PS: The problem with my previous email was in the gmail vs.
>>>> googlemail domain, as Dirk pointed out (I had had that same
>>>> problem before, but I forgot!).
>>>>
>>>> On 22 April 2010 13:17, Romain Francois<romain at r-enthusiasts.com>
> wrote:
>>>>> Thank you for reposting here.
>>>>>
>>>>> It is not trivial to see what is happening in your example, so
>>>>> I'll just give you some tools.
>>>>>
>>>>> The old api (which the classicRcppMatrixExample example uses)
>>>>> does not have
>>>>> support for complex vectors or matrices.
>>>>>
>>>>> The new api does have support for complex vectors and complex
>>>>> matrices. The
>>>>> unit test file runit.ComplexVector.R does indeed contain some
>>>>> very basic examples of using ComplexVector, but not complex
>>>>> matrices. However, you can
>>>>> use Rcpp::ComplexMatrix.
>>>>>
>>>>> Here is an example that calculates the sum of the real part of
>>>>> the elements
>>>>> of a complex matrix diagonal and the sum of the imaginary part:
>>>>>
>>>>> require( Rcpp )
>>>>> require( inline)
>>>>>
>>>>> fx<- cfunction( signature( x = "matrix" ), '
>>>>> /* grab the R object as a complex matrix */
>>>>> ComplexMatrix m(x) ;
>>>>> double re_sum = 0.0 ;
>>>>> double im_sum = 0.0 ;
>>>>> for( int i=0; i<m.ncol(); i++){
>>>>> re_sum += m(i,i).r ;
>>>>> im_sum += m(i,i).i ;
>>>>> }
>>>>> return List::create(
>>>>> _["sum real part"] = re_sum,
>>>>> _["sum imag part"] = im_sum
>>>>> ) ;
>>>>>
>>>>> ', Rcpp = TRUE, includes = "using namespace Rcpp;" )
>>>>>
>>>>> x<- diag( (1-2i)*1:5 )
>>>>> fx( x )
>>>>>
>>>>> Let us know if this gives you enough to get started.
>>>>>
>>>>> Romain
>>>>>
>>>>> Le 22/04/10 12:59, baptiste auguie a écrit :
>>>>>> Dear all,
>>>>>>
>>>>>> I'm hoping to port some R code to C++ to make it faster. The
>>>>>> code makes heavy use of matrices of complex numbers, and playing
>>>>>> with the RcppExamples package this morning I got the impression
>>>>>> that it's not currently implemented in Rcpp. I basically took
>>>>>> the example from classicRcppMatrixExample and tried to change
>>>>>> the types from double to complex. I must confess that I don't
>>>>>> know C++, so maybe I missed something obvious.
>>>>>>
>>>>>> Attached is my dummy example, as well as the R code I'm trying
>>>>>> to port to give you an idea. Any suggestions would be greatly
>>>>>> appreciated!
>>>>>>
>>>>>> Best regards,
>>>>>>
>>>>>> baptiste
>>>>>>
>>>>>>
>>>>>> PS: This message initially failed to reach the list; in the
>>>>>> meantime I got the suggestion from Romain and Dirk to have a
>>>>>> look at the class Rcpp::ComplexMatrix and the example in
>>>>>> runit.ComplexVector.R
>>>>>
>>>>> --
>>>>> Romain Francois
>>>>> Professional R Enthusiast
>>>>> +33(0) 6 28 91 30 30
>>>>> http://romainfrancois.blog.free.fr
>>>>>
>>>>> |- http://bit.ly/9aKDM9 : embed images in Rd documents
>>>>> |- http://tr.im/OIXN : raster images and RImageJ
>>>>> |- http://tr.im/OcQe : Rcpp 0.7.7
>>>
>>> --
>>> Romain Francois
>>> Professional R Enthusiast
>>> +33(0) 6 28 91 30 30
>>> http://romainfrancois.blog.free.fr
>>>
>>> |- http://bit.ly/9aKDM9 : embed images in Rd documents
>>> |- http://tr.im/OIXN : raster images and RImageJ
>>> |- http://tr.im/OcQe : Rcpp 0.7.7
>>
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--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/9aKDM9 : embed images in Rd documents
|- http://tr.im/OIXN : raster images and RImageJ
|- http://tr.im/OcQe : Rcpp 0.7.7
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