Rob Pike's Rules of Programming (1989)

1. 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.

Pike's rules 1 and 2 restate Tony Hoare'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".