function call overhead
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
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