Rob_Pike's 5 Rules of Programming
- Rule 1. You can't tell where a program is going to spend its time. Bottlenecks occur in surprising places, so don't try to second guess and put in a speed hack until you've proven that's where the bottleneck is.
- Rule 2. Measure. Don't tune for speed until you've measured, and even then don't unless one part of the code overwhelms the rest.
- Rule 3. Fancy algorithms are slow when n is small, and n is usually small. Fancy algorithms have big constants. Until you know that n is frequently going to be big, don't get fancy. (Even if n does get big, use Rule 2 first.)
- Rule 4. Fancy algorithms are buggier than simple ones, and they're much harder to implement. Use simple algorithms as well as simple data structures.
- Rule 5. Data dominates. If you've chosen the right data structures and organized things well, the algorithms will almost always be self-evident. Data structures, not algorithms, are central to programming.
Pike's rules 1 and 2 restate ~Tony_Hoare~ Donald_Knuth's famous maxim "Premature optimization is the root of all evil."
Ken_Thompson rephrased Pike's rules 3 and 4 as "When in doubt, use brute force.".
Rules 3 and 4 are instances of the design philosophy KISS.
Rule 5 was previously stated by Fred_Brooks in The_Mythical_Man-Month. Rule 5 is often shortened to "write stupid code that uses smart objects".