[Rcpp-devel] Rcpp version of %in%

[Romain Francois]

Le 15/11/12 17:52, Romain Francois a écrit :
> Hello,
>
> I've commited an Rcpp version of %in%.
>
> For example:
>
> require(Rcpp)
> require(microbenchmark)
>
> sourceCpp( code = '
> #include <Rcpp.h>
> using namespace Rcpp ;
>
> // [[Rcpp::export]]
> LogicalVector in_( CharacterVector x, CharacterVector table){
>      return in( x, table ) ;
> }
> ' )
> `%in++%` <- in_

Could have written as:

sourceCpp( code = '
#include <Rcpp.h>
using namespace Rcpp ;

// [[Rcpp::export("%in++%")]]
LogicalVector in_( CharacterVector x, CharacterVector table){
     return in( x, table ) ;
}
' )

>  > c("a", "ad") %in++% letters
> [1]  TRUE FALSE
>
> In terms of performance:
>
>  > xx <- sample( sample(letters, 15 ), 1000000, replace = TRUE )
>  > microbenchmark(
> +     xx %in% letters,
> +     xx %in++%  letters,
> +     in_( xx, letters )
> + )
> Unit: milliseconds
>                 expr      min       lq   median       uq      max
> 1  in_(xx, letters) 12.79488 12.85228 12.88214 15.33067 44.65161
> 2   xx %in% letters 31.96431 34.43951 34.90381 35.37460 65.68226
> 3 xx %in++% letters 12.81114 12.86457 12.91557 15.06667 16.20493
>
>
>
> The tool here is unordered_set as we don't care where the data is on the
> table, we just want to know if it is there.
>
> Might be interesting at some point to check alternatives to the standard
> hasing functions... e.g. play with sparsehash:
> http://code.google.com/p/sparsehash/
>
> Romain
>


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