What are the best practices for using std::unordered_map in C++11?

What are the best practices for using std::unordered_map in C++11?

When using std::unordered_map in C++11, consider the following best practices: 1. Choose the right hash function for your keys. 2. Use emplace() instead of insert() for better performance. 3. Reserve space if you know the number of elements in advance to avoid reallocations.

Can you explain why using emplace() is better than insert()?

Certainly! emplace() constructs the element in place, which can avoid unnecessary copies or moves, making it more efficient than insert(), which requires creating a temporary object.

What should I consider when choosing a hash function?

When choosing a hash function, consider its distribution, speed, and how well it minimizes collisions. A good hash function will evenly distribute keys across the buckets.

Are there any performance concerns I should be aware of?

Yes, performance can be affected by the load factor and the quality of the hash function. A high load factor can lead to more collisions, which degrades performance.

How can I measure the performance of my unordered_map?

You can measure performance by analyzing the time complexity of operations like insertions, deletions, and lookups, and by profiling your code to identify bottlenecks.