[Automation] Computation time increases with every image done, regardless of starting z position. It's some issue with calling .propagate again for new frames without restarting.

[LtqxWYEG]

I have been making a program for creating a animation. Currently, my code is thus:
(It starts randomly on 17cm, because I've been executing multiple .py programs for cheap-and-easy multithread "support", and this is one of 11.)

... python
diffractsim.set_backend("CPU")  # because I am blessed with a AMD GPU
...
irrelevant stuff, config etc....
...
F = PolychromaticField(
        spectrum= 1 * cf.illuminant_d65, extent_x= 30 * mm, extent_y= 30 * mm, Nx= 2400, Ny= 2400,
        spectrum_size= 400, spectrum_divisions= 400)  # by default spectrum has a size of 400. If new size, we interpolate

# Add (camera) lens with focal length f?
F.add(Lens(f= 80*cm))
# propagate field to z position or something
F.propagate(17*cm)

count = 17
steps = 1
distance = 24
while count <= distance:
    # plot colors (reconstructed image) at z = 80*cm (Fourier plane)
    rgb = F.get_colors()
    #F.plot_colors(rgb, figsize = (16, 16))
    if count < 10:
        imagefile = "./animation/frame_000" + str(count) + ".png"
    elif count < 100:
        imagefile = "./animation/frame_00" + str(count) + ".png"
    elif count < 1000:
        imagefile = "./animation/frame_0" + str(count) + ".png"
    elif count < 10000:
        imagefile = "./animation/frame_" + str(count) + ".png"
    print(imagefile + " done")
    F.save_plot(rgb, figsize= (16, 16), path= imagefile, tight= True)
    F.propagate(0.01)  # In meters --- trying to fix floating point imprecision, resulting in "8.000000000001 cm". --- Didn't work
    count += 1

(
    ffmpeg  # pip install ffmpeg-python // Put ffmpeg.exe in same folder (or maybe in a path variable)
    .input('./animation/frame_%04d.png', framerate=24)  # Note: pattern_type='glob' and "*" wildcard only works in linux
    .output('./animation/animation.mp4')
    .run(overwrite_output=True)
)

results in:

100% |########################################################################|
Computation Took 2611.535078525543
./animation/frame_0017.png done
100% |########################################################################|
Computation Took 3317.8141679763794
./animation/frame_0018.png done
100% |########################################################################|
Computation Took 4478.07142162323
./animation/frame_0019.png done
100% |########################################################################|
Computation Took 5599.06679558754
./animation/frame_0020.png done
...

same with a simulation with very bad quality:

100% |########################################################################|
Computation Took 9.391652345657349
./animation/frame2_0002.png done
100% |########################################################################|
Computation Took 13.946731328964233
./animation/frame2_0003.png done
100% |########################################################################|
Computation Took 18.43080425262451
./animation/frame2_0004.png done
100% |########################################################################|
Computation Took 22.2238667011261
./animation/frame2_0005.png done
100% |########################################################################|
Computation Took 26.535937309265137
./animation/frame2_0006.png done
100% |########################################################################|
Computation Took 30.913010120391846
./animation/frame2_0007.png done
100% |########################################################################|
Computation Took 35.39558458328247
./animation/frame2_0008.png done
100% |########################################################################|
Computation Took 39.53465270996094
./animation/frame2_0009.png done
100% |########################################################################|
Computation Took 44.112547397613525
./animation/frame2_0010.png done
100% |########################################################################|
Computation Took 47.73128795623779
./animation/frame2_0011.png done
100% |########################################################################|
Computation Took 51.79185438156128
./animation/frame2_0012.png done

Why does the computation time increase so much - in all 11 programs I have running at the same time, starting from a different point in z, all taking similar time for their respective first, second, third ... frame.
If I would start a new instance for frame_0020.png now, it would only take about 2611s, not 5599 seconds.
That's not a cumulative time measurement function, btw. Every comp takes progressively longer.

There must be some issue with calling .propagate again after every computation.

How did you, @rafael-fuente, make your animations? Please share :)
kind regards