Can you explain how 10^18 FLOPS is fundamentally different than (10^18 - 20) FLOPS? Do the conventional rules of computing completely change at that exact number?
See this for example. Different applications have different scales at which they reach similar problems. Exascale is decent upper bound for most of the fields. If you really dig in deep, the bound may be found at slightly lower value > 500 Pflops. But it's a good rule of thumb to consider 1 EFlop/s to be safe.
