[Rd] :: and ::: as .Primitives?

luke-tierney at uiowa.edu luke-tierney at uiowa.edu
Thu Jan 22 20:44:13 CET 2015

I'm not convinced that how to make :: faster is the right question. If
you are finding foo::bar being called often enough to matter to your
overall performance then to me the question is: why are you calling
foo::bar more than once? Making :: a bit faster by making it a
primitive will remove some overhead, but your are still left with a
lot of work that shouldn't need to happen more than once.

For default methods there ought to be a way to create those so the
default method is computed at creation or load time and stored in an
environment. For other cases if I want to use foo::bar many times, say
in a loop, I would do

foo_bar <- foo::bar

and use foo_bar, or something along those lines.

When :: and ::: were introduce they were intended primarily for
reflection and debugging, so speed was not an issue. ::: is still
really only reliably usable that way, and making it faster may just
encourage bad practice. :: is different and there are good arguments
for using it in code, but I'm not yet seeing good arguments for use in
ways that would be performance-critical, but I'm happy to be convinced
otherwise. If there is a need for a faster :: then going to a
SPECIALSXP is fine; it would also be good to make the byte code
compiler aware of it, and possibly to work on ways to improve the
performance further e.g. through cacheing.



On Thu, 22 Jan 2015, Peter Haverty wrote:

> Hi all,
> When S4 methods are defined on base function (say, "match"), the
> function becomes a method with the body "base::match(x,y)". A call to
> such a function often spends more time doing "::" than in the function
> itself.  I always assumed that "::" was a very low-level thing, but it
> turns out to be a plain old function defined in base/R/namespace.R.
> What would you all think about making "::" and ":::" .Primitives?  I
> have submitted some examples, timings, and a patch to the R bug
> tracker (https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=16134).
> I'd be very interested to hear your thoughts on the matter.
> Regards,
> Pete
> ____________________
> Peter M. Haverty, Ph.D.
> Genentech, Inc.
> phaverty at gene.com
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

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