R devel - Apr 2010 - Resolving functions using R's namespace mechanism can double runtime

It appears that the runtime for an R script can more than double if a few
references to a function foo() are replaced by more explict references
of the form pkgname::foo().

The more explicit references are of course required when two
loaded packages define the same function.

I can understand why use of this mechanism is not free in an
interpreted environment like R, but the cost seems rather high.

Dominick

	[[alternative HTML version deleted]]

On 4/27/10 1:16 PM, Dominick Samperi wrote:
> It appears that the runtime for an R script can more than double if a few
> references to a function foo() are replaced by more explict references
> of the form pkgname::foo().
>
> The more explicit references are of course required when two
> loaded packages define the same function.
>
> I can understand why use of this mechanism is not free in an
> interpreted environment like R, but the cost seems rather high.
`::` is a function, so there is going to be overhead.  OTOH, there is no 
reason to pay for the lookup more than once.  For example at startup, 
you could do:

myfoo <- pkgname::foo

And then later call myfoo() and I don't think you will see the added cost.

You can formalize the above approach in package code by renaming 
function in the importFrom directive where I believe you can do:

importFrom(pkgname, myfoo=foo)


+ seth

-- 
Seth Falcon | @sfalcon | http://userprimary.net/

Le 27/04/10 22:16, Dominick Samperi a ?crit :
> It appears that the runtime for an R script can more than double if a few
> references to a function foo() are replaced by more explict references
> of the form pkgname::foo().
It would probably help your question if you provide some benchmarks.

a::b is just a shortcut for `::`( a, b ).
> The more explicit references are of course required when two
> loaded packages define the same function.
Not really. You can :
- resolve once: my_foo <- pkgname::foo
- import the variable into your namespace using the importFrom namespace 
directive.
> I can understand why use of this mechanism is not free in an
> interpreted environment like R, but the cost seems rather high.
>
> Dominick
-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
|- http://bit.ly/9aKDM9 : embed images in Rd documents
|- http://tr.im/OIXN : raster images and RImageJ
|- http://tr.im/OcQe : Rcpp 0.7.7