Symmetry-Based Search Space Reduction For Grid Maps

TL;DR

This paper introduces a symmetry-based technique that significantly accelerates optimal pathfinding on grid maps by reducing the search space through decomposition into rectangles and adding macro-edges, while maintaining optimality.

Contribution

The paper presents a novel symmetry-based search space reduction method that speeds up pathfinding on grid maps without sacrificing optimality or completeness.

Findings

Speed up pathfinding by up to 38 times

Reduces memory usage and computational effort

Maintains provable optimality and completeness

Abstract

In this paper we explore a symmetry-based search space reduction technique which can speed up optimal pathfinding on undirected uniform-cost grid maps by up to 38 times. Our technique decomposes grid maps into a set of empty rectangles, removing from each rectangle all interior nodes and possibly some from along the perimeter. We then add a series of macro-edges between selected pairs of remaining perimeter nodes to facilitate provably optimal traversal through each rectangle. We also develop a novel online pruning technique to further speed up search. Our algorithm is fast, memory efficient and retains the same optimality and completeness guarantees as searching on an unmodified grid map.