[Rd] Request: Increasing MAX_NUM_DLLS in Rdynload.c

[Martin Maechler]

>>>>> Steve Bronder <sbronder at stevebronder.com>
>>>>>     on Tue, 20 Dec 2016 01:34:31 -0500 writes:

    > Thanks Henrik this is very helpful! I will try this out on our tests and
    > see if gcDLLs() has a positive effect.

    > mlr currently has tests broken down by learner type such as classification,
    > regression, forecasting, clustering, etc.. There are 83 classifiers alone
    > so even when loading and unloading across learner types we can still hit
    > the MAX_NUM_DLLS error, meaning we'll have to break them down further (or
    > maybe we can be clever with gcDLLs()?). I'm CC'ing Lars Kotthoff and Bernd
    > Bischl to make sure I am representing the issue well.

This came up *here* in May 2015
and then May 2016 ... did you not find it when googling.

Hint:  Use  
       site:stat.ethz.ch MAX_NUM_DLLS
as search string in Google, so it will basically only search the
R mailing list archives

Here's the start of that thread :

  https://stat.ethz.ch/pipermail/r-devel/2016-May/072637.html

There was not a clear conclusion back then, notably as
Prof Brian Ripley noted that 100 had already been an increase
and that a large number of loaded DLLs decreases look up speed.

OTOH (I think others have noted that) a large number of DLLs
only penalizes those who *do* load many, and we should probably
increase it.

Your use case of "hyper packages" which load many others
simultaneously is somewhat convincing to me... in so far as the
general feeling is that memory should be cheap and limits should
not be low.

(In spite of Brian Ripleys good reasons against it, I'd still
 aim for a *dynamic*, i.e. automatically increased list here).

Martin Maechler

    > Regards,

    > Steve Bronder
    > Website: stevebronder.com
    > Phone: 412-719-1282
    > Email: sbronder at stevebronder.com


    > On Tue, Dec 20, 2016 at 1:04 AM, Henrik Bengtsson <
    > henrik.bengtsson at gmail.com> wrote:

    >> On reason for hitting the MAX_NUM_DLLS (= 100) limit is because some
    >> packages don't unload their DLLs when they being unloaded themselves.
    >> In other words, there may be left-over DLLs just sitting there doing
    >> nothing but occupying space.  You can remove these, using:
    >> 
    >> R.utils::gcDLLs()
    >> 
    >> Maybe that will help you get through your tests (as long as you're
    >> unloading packages).  gcDLLs() will look at base::getLoadedDLLs() and
    >> its content and compare to loadedNamespaces() and unregister any
    >> "stray" DLLs that remain after corresponding packages have been
    >> unloaded.
    >> 
    >> I think it would be useful if R CMD check would also check that DLLs
    >> are unregistered when a package is unloaded
    >> (https://github.com/HenrikBengtsson/Wishlist-for-R/issues/29), but of
    >> course, someone needs to write the code / a patch for this to happen.
    >> 
    >> /Henrik
    >> 
    >> On Mon, Dec 19, 2016 at 6:01 PM, Steve Bronder
    >> <sbronder at stevebronder.com> wrote:
    >> > This is a request to increase MAX_NUM_DLLS in Rdynload.c in from 100 to
    >> 500.
    >> >
    >> > On line 131 of Rdynload.c, changing
    >> >
    >> > #define MAX_NUM_DLLS 100
    >> >
    >> >  to
    >> >
    >> > #define MAX_NUM_DLLS 500
    >> >
    >> >
    >> > In development of the mlr package, there have been several episodes in
    >> the
    >> > past where we have had to break up unit tests because of the "maximum
    >> > number of DLLs reached" error. This error has been an inconvenience that
    >> is
    >> > going to keep happening as the package continues to grow. Is there more
    >> > than meets the eye with this error or would everything be okay if the
    >> above
    >> > line changes? Would that have a larger effect in other parts of R?
    >> >
    >> > As R grows, we are likely to see more 'meta-packages' such as the
    >> > Hadley-verse, caret, mlr, etc. need an increasing amount of DLLs loaded
    >> at
    >> > any point in time to conduct effective unit tests. If  MAX_NUM_DLLS is
    >> set
    >> > to 100 for a very particular reason than I apologize, but if it is
    >> possible
    >> > to increase MAX_NUM_DLLS it would at least make the testing at mlr much
    >> > easier.
    >> >
    >> > I understand you are all very busy and thank you for your time.
    >> >
    >> >
    >> > Regards,
    >> >
    >> > Steve Bronder
    >> > Website: stevebronder.com
    >> > Phone: 412-719-1282
    >> > Email: sbronder at stevebronder.com
    >> >
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    >> >
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    >> > https://stat.ethz.ch/mailman/listinfo/r-devel
    >> 

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