[R] Processing repeated images and memory recovery by GC

[Jan van der Laan]

On 05-09-2025 01:24, Jeff Newmiller via R-help wrote:

> 
> I recommend that you try to start building this example sooner rather than later ... maybe include a link to it or paste it into your next request (email to maintainer? a last gasp post here?) to give whoever has that very narrow set of abilities an incentive to look at it. Not having such an example can make it easier to just skip your request as being too vague and time-consuming to investigate.

And often writing such a minimal example helps in pinpointing the issue 
quite often leading to a solution.

You could start by stripping down your current code. Remove all plotting 
commands: does the problem still exist then it is probably in reading or 
cleaning up the image rasters. Is it just for png's or for all image 
formats? Etc. Another way is 'bottom up': write a script that reads 
images and does nothing with them; does the problem happen there? Then 
start adding stuff until the issue occurs again.

Could it be that you keep opening up new graphics devices without 
closing them? Also split.screen creates a kind of devices that should be 
closed.

HTHT,
Jan





> 
> Note that sending your email in plain text (a setting in your email software) rather than the HTML that this was sent in will help avoid us receiving frustrating glitches in your sample code.
> 
> Google "cran reprex" and read the vignette for further help on making an example.
> 
> On September 4, 2025 3:01:08 PM PDT, Bert Gunter <bgunter.4567 using gmail.com> wrote:
>> As I understand it and you, this kind of specialized technical question is
>> usually not a good fit to this list about general issues in R programming,
>> though someone may respond here of course. Alternatively, you may find it
>> useful to post on one (or some?) of the R SIGS (Special Interest Groups)
>> listed at https://www.r-project.org/mail.html  to see if one of them might
>> be a better fit. (Though some listed there may be inactive). Note also that
>> some R packages dealing with image processing have their own dedicated
>> lists.
>>
>> Happy hunting.
>>
>> Cheers,
>> Bert
>>
>> On Thu, Sep 4, 2025 at 2:17 PM Steve Rowley via R-help <r-help using r-project.org>
>> wrote:
>>
>>> I have a question about repeated image processing and recovering memory via
>>> garbage collection.
>>>
>>> A couple images are displayed simultaneously for analysis, using
>>> split.screen().  I'm looping over a large collection of images, using
>>> jpeg/readJPEG(), png/readPNG(), and caTools/read.gif() to load an image
>>> into memory from a file.  Then I use erase.screen() to erase the previous
>>> image, use plot() to set up a plotting area, and display the image with
>>> rasterImage().  Then the user elects some processing, and we move on to the
>>> next image(s).
>>>
>>> I'm very carefully not holding references to any of the previous images.
>>> GC is indeed happening, but memory quickly fills up.  It certainly *looks*
>>> as though the image memory is not being released: printing out trace info
>>> using mem_used()[[1]] says memory use increases with each image, by about
>>> the image size.  Forcing periodic GC's, measuring memory used before and
>>> after, shows that no memory is recovered.
>>>
>>> Some questions:
>>>
>>> (1) Is it known that processing images in this way will lead to allocating
>>> memory that is not recovered by GC?
>>>
>>> (2) Are there any tools you'd recommend to see exactly *what* is filling up
>>> memory, just in case it's not previous images, but some other problem?
>>>
>>> This is R 4.4.2 (for now).  Running MacOS on an ARM processor.
>>> ___________
>>> Steve Rowley <sgr using alum.mit.edu> Zoom: 839 529 4589
>>> <https://us04web.zoom.us/j/8395294589?pwd=dlQ4MUFHK1NFOCtoZFpUNFRtZ2lSQT09
>>>>
>>> It is very dark & after 2000.  If you continue, you are likely to be eaten
>>> by a bleen.
>>>
>>>          [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> https://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>> 	[[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>