It&#x27;s tough.<p>Pass by reference became de rigeur for high performance systems when we agreed that the message passing overhead represented the plurality of computation time.<p>But pass by reference is shared state, and as we started trying to build systems with threading and for multiple cores the ugly truth about memory coherence on modern processors came out.  It was pretty bad.  Java and later C had to come up with some pretty odd looking compromises to get safety without throwing away all of the speed advantages.