Here's a quote from a book:
In multithreaded programs there is often a division of labor between [zero article] threads. In one common pattern, some threads are producers and some are consumers.
In brief, it's discussing computer programs, which are based on multiple threads of execution.
I wonder why there was used the zero article in front of the word "threads" in the phrase "between threads", while it's obvious that any program can "divide a labor" only between the threads it consists of. That is the threads are quite specific. But by using the zero article the author meant unspecific threads, didn't he/she? How can that be explained?