As you may have inferred, these are just some school projects, with one crate per assignment. In the real world, it would probably be better if bench.rs and matrix.rs each had their own crate. In fact, there are crates that implement benchmarks and matrices much more comprehensively, and likely with better coding practices. Then again, the authors of those crates probably spent more than a week on them, so there you go.
Why host here? I needed the ability to reference code from old crates without copying them into my new ones.