"Arrival", apart from being a great movie, poses an interesting conundrum from the director's perspective.
When in book the main character retells most of the events from some point in the future, accepting the determenistic nature of the universe, in the movie we track her journey from the very beginning, watching her arrive to the point she already was in the beginning of the book.
Now, the change was made to lend more weight to the decision she makes after realizing what kind of knowledge she has. Director thought that it would be more impactful if instead of simply realizing deterministic nature of the universe, she made a choice to accept it. But here is the puzzle. To have the knowledge she uses to make the decision, she has to exist in adeterministic universe. But to make a choice, and for that choice to have actual meaning, she has to exist in a universe where outcome is not determined. So what is more important: knowledge or choice?
Basically, just go and watch that movie if you haven't already.
And don't watch the trailers. Trust me, they will only disappoint and ruin the experience.