[Rcpp-devel] RcppMAtrix<complex> ?
baptiste auguie
baptiste.auguie at googlemail.com
Mon Apr 26 22:55:20 CEST 2010
Thank you both for the valuable info, I am looking forward to trying
this out as soon as I can (i've had no time in the past few days).
All the best,
baptiste
On 26 April 2010 10:09, Romain Francois <romain at r-enthusiasts.com> wrote:
> 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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