6 ms·

One reason why unordered map is slow is that it has to be a chained hash map due to the spec not allowing iterator invalidation when resizing.

• aidenn0 7y ago
  that's certainly annoying...
• bertr4nd 7y ago
  I believe unordered_map does invalidate integrators on resize, but does not invalidate references to keys/data, which means the data can’t be stored inline with the hash table structure.