The runtime doesn't need to figure anything out.

If both operands to any, non-serialising, binary operator are non-simple variables (there'd be no chance for concurrency if either is), and the methods which produce those operands are marked (by their authors) as being parallelisable, then the runtime can parallelise them.

The very fact that they are parallelisable and the programmer has placed them within the same (simple)expression, either side of a non-serialising operator, means that the runtime can call the threaded versions of both methods and wait for them both to complete before continuing.

But, for that to be workable, the programmer must be able to guarentee the execution order of the derivation of any parameters that will be passed to those two methods.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco.
Rule 1 has a caveat! -- Who broke the cabal?

In reply to Re^38: Why is EO undefined? (More details!) by BrowserUk
in thread Why is the execution order of subexpressions undefined? by BrowserUk

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