What is nonius?
Nonius is an open-source framework for benchmarking small snippets of C++ code. It is very heavily inspired by Criterion, a similar Haskell-based tool. It runs your code, measures the time it takes to run, and then performs some statistical analysis on those measurements.
The library is header-only so you don’t have to build it. It comes as a single header that you can drop somewhere and #include it in your code. Grab that header from the releases page.