[Rd] function call overhead

[Dominick Samperi]

On Wed, Feb 16, 2011 at 1:13 PM, Paul Gilbert
<pgilbert at bank-banque-canada.ca> wrote:
> (subject changed from: RE: [Rd] Avoiding name clashes: opinion on best practice naming  conventions)
>
> Dominick,
>
> Is this really true? Is there a speed advantage to defining a local function this way, say, within another function, and then calling it within a loop rather than the original? Do you have data on this?
>
> Paul

I worked on an application where a complex characteristic function was
computed over
and over again to compute a Fourier transform, and there was a very
significant performance
penalty to be paid by using myPgk::foo() compared with foo(). It was
recommended on this
list that I try the local assignment trick and it worked great.

Unfortunately this discourages the use of programming styles that are
more explicit and
easier to follow for the human reader. It also complicates the problem
of explicitly specifying
what version of "foo()" you really mean to use.

Dominick

>> -----Original Message-----
>> From: r-devel-bounces at r-project.org [mailto:r-devel-bounces at r-
>> project.org] On Behalf Of Dominick Samperi
>> Sent: February 16, 2011 12:44 PM
> ...
>> Since the resolution of myPkg::foo() occurs at runtime (via a function
>> call) instead
>> of at compile time (as it would in C++), this practice can introduce a
>> significant
>> performance hit. This can be avoided by doing something like:
>> mylocalfunc <- myPkg::foo
>> [tight loop that uses mylocalfunc repeatedly]
>>
>> Here mylocalfunc would not be exported, of course.
>>
>> Dominick
> ...
> ====================================================================================
>
> La version française suit le texte anglais.
>
> ------------------------------------------------------------------------------------
>
> This email may contain privileged and/or confidential information, and the Bank of
> Canada does not waive any related rights. Any distribution, use, or copying of this
> email or the information it contains by other than the intended recipient is
> unauthorized. If you received this email in error please delete it immediately from
> your system and notify the sender promptly by email that you have done so.
>
> ------------------------------------------------------------------------------------
>
> Le présent courriel peut contenir de l'information privilégiée ou confidentielle.
> La Banque du Canada ne renonce pas aux droits qui s'y rapportent. Toute diffusion,
> utilisation ou copie de ce courriel ou des renseignements qu'il contient par une
> personne autre que le ou les destinataires désignés est interdite. Si vous recevez
> ce courriel par erreur, veuillez le supprimer immédiatement et envoyer sans délai à
> l'expéditeur un message électronique pour l'aviser que vous avez éliminé de votre
> ordinateur toute copie du courriel reçu.
>