c++ switch Vs hash map optimization

• cost(Hash_table) >> cost(direct_lookup_table)
• cost(direct_lookup_table) ~= cost(switch) if your compiler translates switches into lookup tables. 
• cost(switch) >> cost(direct_lookup_table) (O(N) vs O(1)) if your compiler does not translate switches and use conditionals, but I can't think of any compiler doing this.
• But inlined direct threading makes the code less readable.

https://stackoverflow.com/questions/931890/what-is-more-efficient-a-switch-case-or-an-stdmap