Your Code Is Fast Only If You Are Lucky: A Quicksort Lesson

Your code is fast – if you're lucky

I discovered that modern compilers like Clang only generate optimal branch-free code if you write in a very specific style. My initial Quicksort implementation was surprisingly slow compared to C++ std::sort, but rewriting simple pointer logic into a more idiomatic C form unlocked massive performance gains. This experience proves that code speed often depends on luck and stylistic choices rather than just algorithmic efficiency.

"Modern compilers optimize loops using fast, branch-free instructions - provided you use the right programming style."