You probably won't hit a limit, CPUs are fast and even "slow" Ruby can do quite a lot. If you do hit the limit though, and have exhausted algorithmic improveme

You probably won't hit a limit, CPUs are fast and even "slow" Ruby can do quite a lot. If you do hit the limit though, and have exhausted algorithmic improvements, you've got your Ruby as an acceptance test for your C++ which will make it unimaginably easier to write correctly. If you tried to do it up front you'd blow up the requirements, if you do it after you've profiled your real-world code you may only need a few lines of critical code.