[Rcpp-devel] Rcpp speed

[Christian Gunning]

Two points -

I see inconsistent timings (~10-20% variance between runs) even at
replications = 1e3.  Things seem to smooth out around replications =
5e3.  Romain's use of 1e4 throughout is a good idea.

Also,  += is sugarized and gives a nice example here - Rcpp wins by a
small margin in at least 1 case:

require(Rcpp)
require(inline)

testfun_R  <- function(x,y) x+y

code <- '
NumericVector xx(x);
NumericVector yy(y);
NumericVector zz = xx + yy;
return( zz );
'

code1 <- '
IntegerVector xx(x);
IntegerVector yy(y);
yy += xx ;
return( yy );
'

testfun_Rcpp <- cxxfunction(signature(x="integer", y="integer"),
   body = code, plugin="Rcpp")

testfun1_Rcpp <- cxxfunction(signature(x="integer", y="integer"),
   body = code1, plugin="Rcpp")
testfun_R  <- function(x,y) x+y

nreps=5e3
nn <- as.numeric(1:1e2)
ii <- 1L:1e2L

test1 = benchmark(replications = nreps,
   R = testfun_R(nn,nn),
   Rcpp = testfun_Rcpp(nn, nn),
   Rcpp1 = testfun1_Rcpp(nn, nn),
   Ri = testfun_R(ii,ii),
   Rcppi = testfun_Rcpp(ii, ii),
   Rcpp1i = testfun1_Rcpp(ii, ii)
)

nn <- as.numeric(1:1e5)
ii <- 1L:1e5L
test2 = benchmark(replications = nreps,
   R = testfun_R(nn,nn),
   Rcpp = testfun_Rcpp(nn, nn),
   Rcpp1 = testfun1_Rcpp(nn, nn),
   Ri = testfun_R(ii,ii),
   Rcppi = testfun_Rcpp(ii, ii),
   Rcpp1i = testfun1_Rcpp(ii, ii)
)

> test1; test2
    test replications elapsed  relative user.self sys.self user.child sys.child
1      R         5000   0.043  1.303030     0.044    0.000          0         0
2   Rcpp         5000   1.714 51.939394     1.700    0.016          0         0
3  Rcpp1         5000   1.711 51.848485     1.624    0.080          0         0
6 Rcpp1i         5000   1.689 51.181818     1.664    0.024          0         0
5  Rcppi         5000   1.719 52.090909     1.708    0.012          0         0
4     Ri         5000   0.033  1.000000     0.032    0.000          0         0
    test replications elapsed relative user.self sys.self user.child sys.child
1      R         5000   2.842 1.334899     1.440    1.396          0         0
2   Rcpp         5000  10.371 4.871301     8.949    1.404          0         0
3  Rcpp1         5000   8.298 3.897605     8.232    0.048          0         0
6 Rcpp1i         5000   2.129 1.000000     2.108    0.012          0         0
5  Rcppi         5000  16.212 7.614843    11.585    4.513          0         0
4     Ri         5000   3.067 1.440582     2.208    0.852          0         0


best,
Christian





On Tue, Dec 21, 2010 at 8:31 AM,
<rcpp-devel-request at lists.r-forge.r-project.org> wrote:
> For completeness, below is the full script.  I also changed funRcpp to use
> IntegerVector.
>
> Dirk
>
>
> require(inline)
> funRcpp <- cxxfunction(signature(x="integer", y="integer"),
>                       body = 'IntegerVector xx(x);
>                               IntegerVector yy(y);
>                               IntegerVector zz = xx + yy;
>                               return( zz );',
>                       plugin="Rcpp")
> x <- 1L:3L
> y <- 10L * x
>
> funR <- function(x, y) {
>    z <- x + y
>    return(z)
> }
>
> stopifnot(identical(funR(x, y), funRcpp(x, y)))
>
> library(rbenchmark)
> x <- 1L:10L
> benchmark(replications = 10000,
>          R = x + x, Rfun = funR(x, x), Rcpp = funRcpp(x, x))
>
> x <- 1L:1000L
> benchmark(replications=1000, R = x + x, Rfun = funR(x, x), Rcpp = funRcpp(x, x))
>
> x <- 1L:1000000L
> benchmark(replications=100, R = x + x, Rfun = funR(x, x), Rcpp = funRcpp(x, x))
>
>



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