running time (ms input size figure results of an experimental study on the running time of an algorithm dot with coordinates ( ,tindicates that on an input of size nthe running time of the algorithm was measured as milliseconds (mschallenges of experimental analysis while experimental studies of running times are valuableespecially when finetuning production-quality codethere are three major limitations to their use for algorithm analysisexperimental running times of two algorithms are difficult to directly compare unless the experiments are performed in the same hardware and software environments experiments can be done only on limited set of test inputshencethey leave out the running times of inputs not included in the experiment (and these inputs may be importantan algorithm must be fully implemented in order to execute it to study its running time experimentally this last requirement is the most serious drawback to the use of experimental studies at early stages of designwhen considering choice of data structures or algorithmsit would be foolish to spend significant amount of time implementing an approach that could easily be deemed inferior by higher-level analysis