While developing a loopy belief propagation library I came across a bug that produced this interesting image.

The code that generated the glitch can be found here (and the fix here). I was trying to do image segmentation on a frame from Spongebob, but instead of smoothing out the foreground/background beliefs the beliefs became unstable and flowered into something that looks to me like a figure.

Later I wondered how the beliefs evolved over time, which results in the cellular-automaton-like sequence:

I’m still not completely sure what caused the glitch, but it seems that I previously tried to use int8s with numba.jit and in my case only int32 worked. Maybe an overflow or types not lining up between Cython, Numba, and Numpy.