Premature optimization is the root of all evil

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.  Yet we should not pass up our opportunities in that critical 3%.

– Donald Knuth (fuente, página 8).