Screeps. GPPC. Rectangle expansion A∗ pathfinding for grid maps. Abstract Search speed, quality of resulting paths and the cost of pre-processing are the principle evaluation metrics of a pathfinding algorithm.

In this paper, a new algorithm for grid-based maps, rectangle expansion A∗ (REA∗), is presented that improves the performance of A∗ significantly. REA∗ explores maps in units of unblocked rectangles. All unnecessary points inside the rectangles are pruned and boundaries of the rectangles (instead of individual points within those boundaries) are used as search nodes.
Google search-list group. Amit’s A* Pages.

Introduction to A*
In games we often want to find paths from one location to another.

We’re not just trying to find the shortest distance; we also want to take into account travel time. Move the blob (start point) and cross (end point) to see the shortest path. To find this path we can use a graph search algorithm, which works when the map is represented as a graph. A* is a popular choice for graph search. Breadth First Search is the simplest of the graph search algorithms, so let’s start there, and we’ll work our way up to A*.
JPS: Fast A* Pathfinding for Uniform Cost Grids. JPS+: discussion. Potential Search Algorithm. JPS Explained. <p><strong>Please note:</strong> this post contains SVG diagrams rendered with javascript.

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</p> There are several related algorithms for finding the shortest path on a uniform-cost 2D grid. The A* algorithm is a common and straightforward optimization of breadth-first (Dijkstra’s) and depth-first searches. There are many extensions to this algorithm, including D*, HPA*, and Rectangular Symmetry Reduction, which all seek to reduce the number of nodes required to find a best path.
PF for grid-based games paper. Nathan Sturtevant, University of Denver. 2017Sufficient Conditions for Node Expansion in Bidirectional Heuristic Search, Jurgen Eckerle, Jingwei Chen, Nathan Sturtevant, Sandra Zilles and Robert Holte, International Conference on Automated Planning and Scheduling (ICAPS) [.bib] Value Compression of Pattern Databases, Nathan R.

Sturtevant, Ariel Felner and Malte Helmert, AAAI Conference on Artificial Intelligence [.bib] Using Hierarchical Constraints to Avoid Conflicts in Multi-Agent Pathfinding, Thayne T. Walker, David Chan and Nathan R.
Trees pathfinding.