Rust code is not being compiled with -O as claimed, and this is slowing down Rust submissions dramatically, making Rust unusable for many problems. 
See Bug report: Rust code is being compiled in debug mode without optimization for reproducible proof. I’ve gotten no response yet from my report to bugs@. (Edit: Actually I got a reasonably quick “we’ll look into this” response that landed in my spam folder, but that’s all so far.)