Are/have any of the authors been active here? In particular, it would be great to get some clarification on these statements:
Consequently, much of the information one can find in online forums and documentation is no longer valid
There is a large amount of documentation available, but it sometimes feels opaque—for instance we were unable to find information on the thread layer used for the multi-threading package.
Also, using globals is mentioned as a performance trap so often that not accounting for them and then claiming poor performance seems suspect. If nothing else, it makes this section sound like a cop-out:
In our case, both programmers have strong prior experience with C and parallel computing and little to intermediate prior knowledge of Python, Julia and Chapel. As detailed in Section 4, we have followed a protocol that aims at making the comparison fair. However, we cannot completely exclude that some parts of the code could be written more efficiently or concisely.