[bruce343434]

You skimmed too fast, from that same article:

> We say that an instruction x precedes an instruction y, sometimes denoted x ? y, if x must complete before y can begin. In a diagram for the dag, x ? y means that there is a positive-length path from x to y. If neither x ? y nor y ? x, we say the instructions are in parallel, denoted x ? y. The figure below illustrates a multithreaded dag:

[Jtsummers]

That quote presents exactly the confusion for GP. x ? y is described to mean both that x precedes y and that x and y are in parallel. It suggests that something got lost in translation here.

https://www.cprogramming.com/parallelism.html

Non-archive link: x < y (x precedes y) and x | y (x is parallel with y).