[R] Lazy loading... advices

Martin Maechler maechler at stat.math.ethz.ch
Sat Oct 16 21:17:22 CEST 2004

>>>>> "UweL" == Uwe Ligges <ligges at statistik.uni-dortmund.de>
>>>>>     on Sat, 16 Oct 2004 18:31:29 +0200 writes:

    UweL> Philippe Grosjean wrote:
    >> Hello,
    >> I am looking for more information about lazy loading
    >> introduced in R 2.0.0.  Doing ?lazyLoad I got some and
    >> there is a 'see also' section that points to
    >> 'makeLazyLoading'... But I cannot reach this page.
    >> My problem is: I recompiled a library

    UweL> Philippe,

    UweL> citing Doug Bates: "Someone named Martin Maechler will
    UweL> shortly be sending you email regarding the distinction
    UweL> between 'library' and 'package'". ;-)

of course, now I have to .... 

Note that library(<package>) attaches and loads a *package* from
one of possibly several libraries { = the directories listed,
e.g., by .libPaths() !} 

    >> that uses a lot of functions from other libraries (of
    >> course I can give details if needed). I load it in my
    >> computer: library(svGUI), and it takes something like 20
    >> seconds to load. In R 1.9.1 it took 3-4 seconds on the
    >> same machine (Windows XP). So, I try now to understand
    >> the mechanism and to find a way to lower the loading time
    >> of this library with lazy loading (its goal is to load
    >> faster, isn't, so I probably do something wrong).

    UweL> It might not always be faster. See Brian Ripley's
    UweL> article in the most recent R Newsletter. Probably you
    UweL> are using a lot of functions in the startup directly
    UweL> after the call to library() (in .First.lib() or
    UweL> .onLoad() or Hooks or whatever).  I think you want to
    UweL> specify "LazyLoad: no" in the package's DESCRIPTION
    UweL> file (cp. "Writing R Extensions").

I'm pretty sure the increased startup time comes from the very
long 'Depends:' field in Philippe's package.
I'd bet that -- after reading Brian's article -- Philippe will
find that he can make the 'Depends' much smaller, e.g., by
moving entries to 'Suggests'.


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