TITLE: What does this "double less than or equals to" sign mean?
QUESTION [12 upvotes]: I found this in a Computer Science pseudocode context (see page 4 of this paper).

REPLY [5 votes]: I add a comment for the sake of completeness. As said, in general $\geqq$ means $\geq$, but in some old math texts it is possible to find the following distinction for a real vector $x$:

"Positive" denoted as $x > 0$: all the elements of $x$ are strictly positive;
"Semipositive" denoted as $ x \geq 0$: all the elements of $x$ are nonnegative but at least one of them is strictly positive;
"Nonnegative" denoted as $ x \geqq 0$: all the elements of $x$ are nonnegative.

In other terms, with this notation, $x \geq 0$ implies $x \neq 0$.