Nice article!

What surprises me is that the original VLC filter does not use SIMD. Sometimes I wonder why I spent my money on a "modern" CPU with a lot of new features that stay completely ignored by most software I run every day.

The C# version uses unsafe raw pointers which is practically the same as writing it in C. No surprise then that the outcomes are similar.

I would have expected the filters to run as a shader on the GPU which would make them much more efficient. I remember implementing two-pass gaussian blur in GLSL almost 20 years ago.

There are much faster algorithms available for Gaussian blur though, running in O(n) rather than O(nσ) for an n pixel image and radius σ. See https://www.ipol.im/pub/art/2013/87/article.pdf for a survey.

Very interesting readup! I have some C# projects I've had in mind to try to compile to AOT. Quite different for complex programs of course, but the perf being very close to C is a great motivator.

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Most industries consider 8% a mountain. More than their entire profit margin.