1. CPU time, if speed is what we're interested in, is affected by very many factors, many of which are not related to the algorithm itself:
-- which computer -- how heavily is it loaded -- which programming language -- which compiler -- hidden factors can swamp the ones you're trying to measure: -- array-bounds checking -- relative speeds: array indexing, record access and pointer following, -- overhead for procedure calls -- I/O
2.Which test data? It is true that `constant time' algorithms, by definition, take the same amount of time on all inputs. But most algorithms are not constant time so we cannot measure efficiency as a single number; it must be expressed as a function of the input.
Last modified: 27/July/98 (12:14)