Refactoring is very similar to performance optimization, as both involve carrying out code manipulations that don’t change the overall functionality of the program. The difference is the purpose: Refactoring is always done to make the code “easier to understand and cheaper to modify.” This might speed things up or slow things down. With performance optimization, I only care about speeding up the program, and am prepared to end up with code that is harder to work with if I really need that improved performance.
