How do I iterate safely under modification with std::unordered_map in performance-sensitive code?

Iterating over a `std::unordered_map` in C++ can present challenges, especially when the map is being modified concurrently. However, there are safe and efficient strategies to handle such situations in performance-sensitive code.

Use of Iterators

When you need to remove elements from a `std::unordered_map` while iterating over it, the key is to use iterators correctly to ensure you do not invalidate them. You can use the `erase` method to safely remove elements while iterating. Here's how to do this:


        #include 
        #include 

        int main() {
            std::unordered_map myMap = {
                {1, "One"},
                {2, "Two"},
                {3, "Three"}
            };

            for (auto it = myMap.begin(); it != myMap.end(); ) {
                if (it->first % 2 == 0) {
                    it = myMap.erase(it);  // Erase returns the next iterator
                } else {
                    ++it;  // Move to the next element
                }
            }

            for (const auto& pair : myMap) {
                std::cout << pair.first << ": " << pair.second << std::endl;
            }

            return 0;
        }

Concurrent Modifications

For scenarios where modifications can occur concurrently (multiple threads), consider using mutexes or other synchronization mechanisms to prevent data races and ensure thread safety. Using concurrent data structures may also be warranted if performance demands high concurrent access.

How do I iterate safely under modification with std::unordered_map in performance-sensitive code?

Use of Iterators

Concurrent Modifications

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How do I iterate safely under modification with std::unordered_map in performance-sensitive code?

Use of Iterators

Concurrent Modifications

Related Questions

Popular Topics

Recent Languages