The ever present memory bloat with Ruby has been discovered to be a glibc issue. Jemalloc makes MRI memory usage much more predictable and stable.

It's gotten a lot better since then, but so have all the other languages! I still love Ruby but I would use Python for ML in a heartbeat.

I work with Ruby, Python, and R daily.

I use Ruby for everything I can, Python for ML, and R for data analysis. I just find it easier to not swim upstream and force ruby onto all of those contexts when the other 2 languages have loads of inertia behind them in those spaces. It's unfortunate.