This gist lists various C++ 'quick benchmarks' that have been written on quick-bench.com to test/verify various hypotheses. Quick Bench makes use of Google Benchmark.

Reserve in a vector vs not reserve

Cost of data indirection (e.g. direct vs pointer vs pointer-to-pointer)

'Stack vector' vs vector

Cost of using std::function vs lambda and function pointers

Cost of using an std::set for building a list of unique items vs using a std::vector

Lock+unlock for std::mutex vs spinlock implemented with std::atomic and std::atomic_flag (+ recursive implementations)

Applying pre-multiplied alpha to a 1024x1024 image

Lookup of a string key in a key-value container (attempting to run the test for different container sizes)

Populate vectors, maps, etc with data

Add/remove pointers from a vector or list (and assuming we need to find the item to remove in the vector)

Allocating memory on stack vs on heap (including dynamic size on stack)

Map lookup vs Vector search

Accessing a global static variable vs a local static variable vs a mutex-protected variable