The authors do have a comment on the Github project that code needs to be allowed to run for a while so the JIT can kick in, although I didn't see any statement

The authors do have a comment on the Github project that code needs to be allowed to run for a while so the JIT can kick in, although I didn't see any statement of how they did that. The paper also mentions a decision to turn a loop body into a function to allow a JIT to optimize things. But, generally, I'm not interested in whether "for" loops run faster in language X or language Y. I am interested in whether some languages encourage code styles that happen to be easily optimized (I'm also interested in whether some languages encourage code styles that are easily maintained, easily extensible, or easily run into a ditch). This paper is meaningful to somebody, but it's clearly written by people who spend most of their thinking about things other than programming. That's not an insult; it's a simple fact that a lot of programs are written by people who are experts in other fields. I happen to work with a former physicist who has experience writing programs to run on one of the nation's largest supercomputers. The depressing thing (to me) is that while he knows how to write numerical programs that run close to a computer's theoretical maximum speed, that information is only well-known among a small group of people (namely people who have to show that if they're allowed to use a supercomputer, they won't make it run wasteful code). I wish it were shared more broadly.