Who reordered my code?!

There is a hidden problem waiting as Ruby becomes 3x faster and starts to support parallel computation - reordering by JIT compilers and CPUs. In this talk, we’ll start by trying to optimize a few simple Ruby snippets. We’ll play the role of a JIT and a CPU and order operations as the rules of the system allow. Then we add a second thread to the snippets and watch it as it breaks horribly. In the second part, we’ll fix the unwanted reorderings by introducing a memory model to Ruby. We’ll discuss in detail how it fixes the snippets and how it can be used to write faster code for parallel execution.