Displaying 3 results from an estimated 3 matches for "doublethisint".
2015 Mar 02
3
R-devel does not update the C++ returned variables
...s on the size
of the input vector. i + i becomes the winner for longer vectors (e.g. i
<- 1:1e6), but a proper Rcpp version is still approximately twice as fast.
Rcpp::cppFunction("NumericVector doubleThisNum(NumericVector x) {
return(2*x); }")
Rcpp::cppFunction("IntegerVector doubleThisInt(IntegerVector x) {
return(2*x); }")
i <- 1:1e6
mb <- microbenchmark::microbenchmark(doubleThisNum(i), doubleThisInt(i),
i*2, 2*i, i*2L, 2L*i, i+i, times=100)
plot(mb, log="y", notch=TRUE)
> (mb <- microbenchmark(doubleThis(i), i*2, 2*i, i*2L, 2L*i, i+i, times=2^12))
&...
2015 Mar 02
0
R-devel does not update the C++ returned variables
...ithms also depends on the size
> of the input vector. i + i becomes the winner for longer vectors (e.g. i
> <- 1:1e6), but a proper Rcpp version is still approximately twice as fast.
The difference in speed is probably due to the fact that R does safe
arithmetic. C or C++ do not:
> doubleThisInt(i)
[1] 2147483642 2147483644 2147483646 NA -2147483646
-2147483644
> 2L * i
[1] 2147483642 2147483644 2147483646 NA NA NA
Warning message:
In 2L * i : NAs produced by integer overflow
H.
>
> Rcpp::cppFunction("NumericVector double...
2015 Mar 02
3
R-devel does not update the C++ returned variables
On 2 March 2015 at 09:09, Duncan Murdoch wrote:
| I generally recommend that people use Rcpp, which hides a lot of the
| details. It will generate your .Call calls for you, and generate the
| C++ code that receives them; you just need to think about the real
| problem, not the interface. It has its own learning curve, but I think
| it is easier than using the low-level code that you need to