I'd be interested to see at what scale parallel evaluation in Clio beats serial evaluation that has been compiled to native machine code with basic compiler opt

I'd be interested to see at what scale parallel evaluation in Clio beats serial evaluation that has been compiled to native machine code with basic compiler optimizations, for scientific computing (say, solving nonlinear differential equations). My guess is it's enormous, but I could be wrong since contemporary JS engines do quite well with numeric computing. But there's a wealth of scientific computing that can't be magically made to be parallel and the parallel equivalents are often slower due to duplicated arithmetic and overhead in setting up the computation (recursive computations are particularly bad about this) - finding a parallel evaluation strategy that is actually faster is nontrivial. It's really not a safe assumption that parallel = faster.