[R] Processing repeated images and memory recovery by GC

[Bert Gunter]

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.
>
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