The modern meaning for algorithm is quite similar to that of recipe, process, method, technique, procedure, routine, rigmarole, except that the word "algorithm" connotes something just a little different. Besides merely being a finite set of rules that gives a sequence of operations for solving a specific type of problem, an algorithm has five important features:
1)Finittness.
2)Definiteness.
3)Input.
4)Output.
5)Effectiveness.
Performance analysis: machine independent
1)Complexity theory
Space complexity: amount of memory --> a)fixed space(instruction, simple variables, constants). b)memory depends on instance.
Time complexity: amount of computer time --> a)compile time. b)execution time depends on instance.
Performance measurement: machine dependent
1)Asympototic Notation --> Big "Oh"
原文：http://www.cnblogs.com/007beta/p/3844730.html