16 Experiments with the Adaptive Graph Traverser Donald Michie and Robert Ross

A formal description is given of GT 4, a revised and extended version of the Graph Traverser. Methods are described whereby GT4 can improve its performance at run time (a) by automatic optimization of parameters used by the evaluation function and (b) by dynamic re-ordering of operators. Neither method depends upon there being any successful searches in the program's past experience of a given problem. The essential feasibility of both approaches has been validated in experimental tests using sliding block puzzles. Two planned extensions, 'local smoothing' and'regionalization' are described. INTRODUCTION The Graph Traverser (Doran and Michie 1966), and subsequent work based on it, represents an attempt to adapt game-playing methods, particularly those of Samuel (1959), to automatic problem-solving. The design objective is not the simulation of human problem-solving as a study in psychology, but rather to provide an efficient general-purpose search procedure appropriate to non-numerical problem domains. There is a parallel with the development of direct search techniques for numerical function minimization, for example pattern search (Hooke and Jeeves 1961), simplex (Spendley, Hext and Himsworth 1962, Nelder and Mead 1965).