CLOS has :before, :after, and :around qualifiers which Julia doesn't support, and CLOS supports multiple inheritance. Both of these make de virtualization much

CLOS has :before, :after, and :around qualifiers which Julia doesn't support, and CLOS supports multiple inheritance. Both of these make de virtualization much harder. https://arxiv.org/pdf/1411.1607.pdf https://arxiv.org/pdf/1411.1607.pdf is a pretty good general resource for info about Julia's design decisions and has a section on multiple dispatch. The reason that generating more code can be faster is that more code can actually result in fewer cache misses. Julia is so fast because it is really good at inlining, constant prop, and automatic vectorization. These optimizations all increase the amount of generated code, but remove conditionals that decrease code locality.