- 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.) For example, binary trees are always faster than splay trees for workaday problems.
- 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.
The following data structures are a complete list for almost all practical programs: array, linked list, hash table, binary tree.
Of course, you must also be prepared to collect these into compound data structures. For instance, a symbol table might be implemented as a hash table containing linked lists of arrays of characters.
- 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. (See Brooks p. 102.)
- Rule 6. There is no Rule 6.
-- Rob Pike, Programming in C: Complexity
Q&A for professional and enthusiast programmers
Q&A for system and network administrators
Q&A for students, teachers, and linguists wanting to discuss the finer points of the Spanish language
Q&A for power users of Apple hardware and software
Q&A for power users of web applications
Q&A for parents, grandparents, nannies and others with a parenting role
Q&A for computer enthusiasts and power users
Q&A for users of Linux, FreeBSD and other Un*x-like operating systems
Q&A for enthusiasts and power users of the Android operating system
Q&A for professional programmers interested in conceptual questions about software development
Q&A for people studying math at any level and professionals in related fields
Q&A for Ubuntu users and developers