[Rcpp-devel] R vectorisation vs. C++ vectorisation

[Douglas Bates]

On Mon, Nov 19, 2012 at 11:36 AM, Hadley Wickham <h.wickham at gmail.com>wrote:

> > To be fair with the R language, I would have compare with the use of real
> > primitives :
> >
> > vaccBubu <- function(age, female, ily) {
> >     gender <- female * 1.25
> >     gender[!female] <- 0.75
> >     p <- (0.25 + 0.3 * 1 / (1 - exp(0.04 * age)) + 0.1 * ily) * gender
> >     p[p < 0] <- 0
> >     p[p > 1] <- 1
> >     p
> > }
> >
>
> I think you could do it a bit more elegantly with
>
> gender <- 0.75 + female * 0.5
>
> but pmin and pmax are "real" primitives, so I think it's fine to use them.


In the folklore ifelse, pmin and pmax are know to be slow.  I know that
there was some work on pmin and pmax but I think they are still more
sluggish than desired.

In early work on generalized linear mixed models i did some profiling and
discovered that an inordinate amount of time was spent on evaluating the
inverse link, derivative and variance functions and a lot of that could be
traced to pmin and pmax.
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