That's good advice that should be repeated over and over. I see it so often that people don't write clean code because that's considered not efficient but they

That's good advice that should be repeated over and over. I see it so often that people don't write clean code because that's considered not efficient but they don't have any real data. Especially when you deal with optimizing compilers it's often totally counterintuitive where the real bottlenecks are. Obviously you shouldn't be stupid and always shout "premature optimization" but make it a habit to profile from item and time and learn from it.