ERA*: Enhanced Relaxed A* algorithm for solving the shortest path problem in regular grid maps

Abstract

This paper introduces a novel algorithm for solving the point-to-point shortest path problem in a static regular 8-neighbor connectivity (G8) grid. This algorithm can be seen as a generalization of Hadlock algorithm to G8 grids, and is shown to be theoretically equivalent to the relaxed A⁎ (RA⁎) algorithm in terms of the provided solution's path length, but with substantial time and memory savings, due to a completely different computation strategy, based on defining a set of lookup matrices. Through an experimental study on grid maps of various types and sizes (1290 runs on 43 maps), it is proven to be 2.25 times faster than RA⁎ and 17 times faster than the original A⁎, in average. Moreover, it is more memory-efficient, since it does not need to store a G score matrix.