std::map performance issues when using custom comparator in C++17
I'm relatively new to this, so bear with me. I am facing performance issues with a `std::map` in C++17 when using a custom comparator. My comparator is supposed to sort a structure based on multiple fields, but I noticed that the insertion time is significantly higher than expected. I implemented the comparator like this: ```cpp struct CustomComparator { bool operator()(const MyStruct &a, const MyStruct &b) const { if (a.field1 != b.field1) return a.field1 < b.field1; return a.field2 < b.field2; } }; ``` I then create my map like this: ```cpp std::map<MyStruct, int, CustomComparator> myMap; ``` When I insert elements, the time complexity seems to be worse than the expected O(log n) per insertion. After profiling, I found that the `operator()` of my custom comparator is being called excessively. I suspect this might be due to the way I am handling equality checks for the first field. I tried adding a check to see if `field1` is equal before comparing `field2`, but the performance didn't improve. I also verified that `MyStruct` has a proper copy constructor and assignment operator defined. The data is being inserted in a random order, and Iām noticing a lot of rebalancing happening internally. The profiler highlighted that the majority of the time is spent in the comparator. Here's how I'm inserting: ```cpp for (const auto &item : data) { myMap[item] = item.value; } ``` Is there a better way to implement the comparator or optimize the insertions? I want to ensure that Iām using best practices here, as the map has to handle a large number of entries (up to 1 million). Any advice on improving this would be greatly appreciated! Thanks in advance!