[Rcpp-devel] Sparse matrices with RcppArmadillo

[Romain Francois]

Ah. One thing I could do is leverage this:

#ifdef ARMA_EXTRA_SPMAT_PROTO
   #include ARMA_INCFILE_WRAP(ARMA_EXTRA_SPMAT_PROTO)
#endif

Not sure how yet.

Le 08/12/12 19:17, Romain Francois a écrit :
> That looks very similar, if not identical to what dgCMatrix uses. Can
> you direct me to a constructor where I could feed such information ?
>
> Romain
>
> Le 08/12/12 17:35, c s a écrit :
>> Armadillo sparse matrices are stored in Compressed Sparse Column format:
>>
>> http://en.wikipedia.org/wiki/Sparse_matrix#Compressed_sparse_column_.28CSC_or_CCS.29
>>
>>
>> This layout is used by a majority of external solvers.
>>
>> It would be far more efficient to take this layout into account when
>> copying matrices, instead of blindly (and slowly) copying element by
>> element.
>>
>>
>> On Sunday, December 9, 2012, Romain Francois <romain at r-enthusiasts.com
>> <mailto:romain at r-enthusiasts.com>> wrote:
>>  > Le 08/12/12 09:45, Søren Højsgaard a écrit :
>>  >>
>>  >> Dear all,
>>  >>
>>  >> I want to use a matrix (of type "dgCMatrix" from the Matrix package)
>> in RcppArmadillo, so I do:
>>  >>
>>  >> library(inline)
>>  >> src <- '
>>  >> using namespace arma;
>>  >> using namespace Rcpp;
>>  >> SpMat<double> X = as<SpMat<double> >(XX_);
>>  >> '
>>  >> foo <- cxxfunction(signature(XX_=""), body=src,
>> plugin="RcppArmadillo")
>>  >>
>>  >> - but this fails. It seems to me (browsing the web) that SpMat are
>> supported, but I might be wrong here. I have no indication that
>> dgCMatrix matrices can be "converted" to SpMat's. I know that I can work
>> with dgCMatrix matrices with RcppEigen, but what I need is to extract
>> submatrices and that is very easy to do with RcppArmadillo.
>>  >>
>>  >> Any thoughts? Thanks in advance.
>>  >> Regards
>>  >> Søren
>>  >
>>  > Doug might know better about the internals of Matrix types. This is
>> just following the recipee from how these are handled in RcppEigen:
>>  >
>>  > #include <RcppArmadillo.h>
>>  > // [[Rcpp::depends(RcppArmadillo)]]
>>  > using namespace Rcpp ;
>>  >
>>  > // [[Rcpp::export]]
>>  > void convert(S4 mat){
>>  >     IntegerVector dims = mat.slot( "Dim" ) ;
>>  >     IntegerVector i = mat.slot( "i" ) ;
>>  >     IntegerVector p = mat.slot( "p" ) ;
>>  >     NumericVector x = mat.slot( "x" ) ;
>>  >
>>  >     int nrow = dims[0], ncol = dims[1] ;
>>  >     arma::sp_mat res( nrow, ncol) ;
>>  >     for(int j = 0; j < ncol; ++j) {
>>  >         for (int k = p[j]; k < p[j + 1]; ++k) res( i[k], j ) = x[k];
>>  >     }
>>  >     std::cout << res << std::endl ;
>>  >
>>  > }
>>  >
>>  >
>>  > /*** R
>>  >     require(Matrix)
>>  >     i <- c(1,3:8); j <- c(2,9,6:10); x <- 7 * (1:7)
>>  >     ( A <- sparseMatrix(i, j, x = x) )
>>  >
>>  >     convert(A)
>>  > ***/
>>  >
>>  > I don't think there is a better way to fill multiple values ina
>> SpMat, maybe Conrad has insights.
>>  >
>>  > Romain
>>  >
>>  > --
>>  > Romain Francois
>>  > Professional R Enthusiast
>>  > +33(0) 6 28 91 30 30
>>  >
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>>  >
>>  > blog: http://romainfrancois.blog.free.fr
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>>  >
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>>  >
>
>


-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30

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blog:            http://romainfrancois.blog.free.fr
|- http://bit.ly/RE6sYH : OOP with Rcpp modules
`- http://bit.ly/Thw7IK : Rcpp modules more flexible