Choose an algorithm that's reasonably efficient and easy to implement. Then parallelize if it wasn't fast enough. Then try to find a better algorithm. And only

Choose an algorithm that's reasonably efficient and easy to implement. Then parallelize if it wasn't fast enough. Then try to find a better algorithm. And only then vectorize. Pick the low-hanging fruit first, and only resort to options that require more work and make the code less maintainable if that wasn't enough. Software engineers and computer scientists are often reluctant to parallelize their code, because they have learned that it's difficult and full of hidden pitfalls. But then they lose the performance gains from multithreaded loops and other simple approaches, which are often essentially free. Multithreaded code is not particularly difficult or dangerous, as long as you are not trying to be clever.