Knuth Optimization Quotes

Premature optimization is the root of all evil.

Premature optimization is the root of all evil.

If you optimize everything, you will always be unhappy.

premature optimization is the root of all evil. —Donald E. Knuth [

The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; premature optimization is the root of all evil (or at least most of it) in programming.

For software developers who take their work seriously, Knuth is the consummate craftsman. Here’s what he has to say about optimization: Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil.2 (Emphasis added.)

The PLT helped us to understand what our programming instructions were doing along the essential axis of speed and showed us precisely when and where we were introducing slowness to our source code. The PLT told us when to pay attention to the “small efficiencies” Knuth mentioned. It was our 3 percent escape hatch, a way to know for sure that optimization wasn’t “premature.” We were sure each optimization we did was helping to keep performance heading in the right direction.

Seibel: In 1974 you said that by 1984 we would have “Utopia 84,” the sort of perfect programming language, and it would supplant COBOL and Fortran, and you said then that there were indications that such language is very slowly taking shape. It's now a couple of decades since '84 and it doesn't seem like that's happened. Knuth: No. Seibel: Was that just youthful optimism? Knuth: I was thinking about Simula and trends in object-oriented programming when I wrote that, clearly. I think what happens is that every time a new language comes out it cleans up what's understood about the old languages and then adds something new, experimental and so on, and nobody has ever come to the point where they have a new language and then they want to stop at what's understood. They're always wanting to push further. Maybe someday somebody will say, “No, I'm not going to be innovative; I'm just going to be clean and simple, and I'm going to stick to it.” Pascal was started with that philosophy but then didn't continue. Maybe we'll get to a time when somebody will say, “Let's set our sights lower and really try to make something that's going to be stable.” It might be a good idea.