>>>>> Michael Lawrence <lawrence.mich...@gene.com>
>>>>> on Mon, 26 Jan 2015 05:12:55 -0800 writes:
> A isNamespaceLoaded() function would be a useful thing to
> have in general if we are interested in readable code. An
> efficient implementation would be just a bonus.
Good point (readability), and thank you for the support!
Note one slight drawback with your name (which is clearly
better than mine first proposal):
We'd have the three functions named
isBaseNamespace(ns)
isNamespace(ns)
isNamespaceLoaded(name)
where 'name' is really different from 'ns', namely :
> isNamespace("stats")
[1] FALSE
> isNamespace(asNamespace("stats"))
[1] TRUE
but
> isNamespaceLoaded("stats")
[1] TRUE
> isNamespaceLoaded(asNamespace("stats"))
Error in as.vector(x, "symbol") :
cannot coerce type 'environment' to vector of type 'symbol'
>
So, from my (non native English view) a slightly more suggestive
function name may be
isLoadedNamespace(name)
or using Luke's original language, still present in the C code,
isRegisteredNamespace(name)
but I would prefer the former, isLoadedN..S..()
Martin
> On Mon, Jan 26, 2015 at 3:36 AM, Martin Maechler
> <maech...@lynne.stat.math.ethz.ch> wrote:
>>>>>>> Winston Chang <winstoncha...@gmail.com> on Fri, 23
>>>>>>> Jan 2015 10:15:53 -0600 writes:
>>
>> > I think you can simplify a little by replacing this:
>>
>> > pkg %in% loadedNamespaces() > with this: >
>> .getNamespace(pkg)
>>
>> almost: It would be
>>
>> !is.null(.getNamespace(pkg))
>>
>> > Whereas getNamespace(pkg) will load the package if it's
>> not already > loaded, calling .getNamespace(pkg) (note
>> the leading dot) won't load > the package.
>>
>> indeed. And you, Winston, are right that this new code
>> snippet would be an order of magnitude faster :
>>
>>
##-----------------------------------------------------------------------------
>>
>> f1 <- function(pkg) pkg %in% loadedNamespaces() f2 <-
>> function(pkg) !is.null(.getNamespace(pkg))
>>
>> require(microbenchmark)
>>
>> pkg <- "foo"; (mbM <- microbenchmark(r1 <- f1(pkg), r2 <-
>> f2(pkg))); stopifnot(identical(r1,r2)); r1 ## Unit:
>> microseconds ## expr min lq mean median uq max neval cld
>> ## r1 <- f1(pkg) 38.516 40.9790 42.35037 41.7245 42.4060
>> 82.922 100 b ## r2 <- f2(pkg) 1.331 1.8285 2.13874 2.0855
>> 2.3365 7.252 100 a ## [1] FALSE
>>
>> pkg <- "stats"; (mbM <- microbenchmark(r1 <- f1(pkg), r2
>> <- f2(pkg))); stopifnot(identical(r1,r2)); r1 ## Unit:
>> microseconds ## expr min lq mean median uq max neval cld
>> ## r1 <- f1(pkg) 29.955 31.2575 32.27748 31.6035 32.1215
>> 62.428 100 b ## r2 <- f2(pkg) 1.067 1.4315 1.71437 1.6335
>> 1.8460 9.169 100 a ## [1] TRUE loadNamespace("Matrix") ##
>> <environment: namespace:Matrix> pkg <- "Matrix"; (mbM <-
>> microbenchmark(r1 <- f1(pkg), r2 <- f2(pkg)));
>> stopifnot(identical(r1,r2)); r1 ## Unit: microseconds ##
>> expr min lq mean median uq max neval cld ## r1 <- f1(pkg)
>> 32.721 33.5205 35.17450 33.9505 34.6050 65.373 100 b ##
>> r2 <- f2(pkg) 1.010 1.3750 1.93671 1.5615 1.7795 12.128
>> 100 a ## [1] TRUE
>>
>>
##-----------------------------------------------------------------------------
>>
>> Hence, indeed, !is.null(.getNamespace(pkg))
>>
>> seems equivalent to pkg %in% loadedNamespaces()
>>
>> --- when 'pkg' is of length 1 (!!!)
>>
>> but is 20 times faster.... and we have 11 occurrences of
>> ' <...> %in% loadedNamespaces() ' in the "base packages"
>> in the R (devel) sources, 3 in base, 2 in methods, 3 in
>> stats, 2 in tools, 1 in utils..
>>
>> On the other hand, pkg %in% loadedNamespaces()
>>
>> is extremely nicely readable code, whereas
>> !is.null(.getNamespace(pkg)) is pretty much the contrary.
>> .. and well readable code is so much easier to maintain
>> etc, such that in many cases, code optimization with the
>> cost of code obfuscation is *not* desirable.
>>
>> Of course we could yet again use a few lines of C and R
>> code to provide a new R lowlevel function, say
>>
>> is.loadedNamespace()
>>
>> which would be even faster than
>> !is.null(.getNamespace(pkg))
>>
>> ... ...
>>
>> but do we have *any* evidence that this would noticably
>> speedup any higher level function such as library() ?
>>
>>
>> Thank you, again, Winston; you've opened an interesting
>> topic!
>>
>> --
>> Martin Maechler, ETH Zurich
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
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