Why std::unordered_set Underperforms in Performance-Critical C++ Loops
std::unordered_set's O(1) average-case complexity masks significant runtime overhead in performance-critical loops, potentially degrading throughput by an order of magnitude
When tracking visited nodes with dense integer IDs in approximate nearest neighbor algorithms, alternative data structures outperform hash tables in the hottest code paths
Real-world profiling reveals that conventional container choices can be costly; measurement-driven optimization remains essential for performance-sensitive applications