On: A 100x speedup with unsafe Python

[Animats]

That's where you end up after heavy bikeshedding. Lots of features, terrible performance, as the OP points out.

[infogulch → Animats]

I agree with you on sparse arrays and multidimensional slices, but this is basically the same as what you'd do manually. Saying that "track strides for me" is "lots of features" is a bit uncharitable.