D∗ Extra Lite: A Dynamic A∗ with Search-Tree Cutting and Frontier-Gap Repairing

Abstract

Searching for the shortest-path in an unknown or changeable environment is a common problem in robotics and video games, in which agents need to update maps and to perform re-planning in order to complete their missions. D∗ Lite is a popular incremental heuristic search algorithm (i.e., it utilizes knowledge from previous searches). Its efficiency lies in the fact that it re-expands only those parts of the search-space that are relevant to registered changes and the current state of the agent. In this paper, we propose a new D∗ Extra Lite algorithm that is close to a regular A∗, with reinitialization of the affected search-space achieved by search-tree branch cutting. The provided worst-case complexity analysis strongly suggests that D∗ Extra Lite's method of reinitialization is faster than the focused approach to reinitialization used in D∗ Lite. In comprehensive tests on a large number of typical two-dimensional path-planning problems, D∗ Extra Lite was 1.08 to 1.94 times faster than the optimized version of D∗ Lite. Moreover, while demonstrating that it can be particularly suitable for difficult, dynamic problems, as the problem-complexity increased, D∗ Extra Lite's performance further surpassed that of D∗Lite. The source code of the algorithm is available on the open-source basis.