But there's also the not-so-common (yet still somewhat frequent) case where the inputs are highly different. Myers diff alone would take quadratic time, which i

But there's also the not-so-common (yet still somewhat frequent) case where the inputs are highly different. Myers diff alone would take quadratic time, which in practice is often unacceptable. Real-world implementations often have a limit on the amount of difference (e.g. max(256, sqrt(input size))), and if that's exceeded, they switch to heuristics (so the resulting diff is no longer guaranteed to be minimal). This reduces the worst-case runtime from O(N*2) to O(N*1.5).