A* Algorithm for very large graphs, any thoughts on caching shortcuts?

Question

I\'m writing a courier/logistics simulation on OpenStreetMap maps and have realised that the basic A* algorithm as pictured below is not going to be fast enough for large maps (

Answer 1

GraphHopper does two things more to get fast, none-heuristic and flexible routing (note: I'm the author and you can try it online here)

1. A not so obvious optimization is to avoid 1:1 mapping of OSM nodes to internal nodes. Instead GraphHopper uses only junctions as nodes and saves roughly 1/8th of traversed nodes.
2. It has efficient implements for A*, Dijkstra or e.g. one-to-many Dijkstra. Which makes a route in under 1s possible through entire Germany. The (none-heuristical) bidirectional version of A* makes this even faster.

So it should be possible to get you fast routes for greater London.

Additionally the default mode is the speed mode which makes everything an order of magnitudes faster (e.g. 30ms for European wide routes) but less flexible, as it requires preprocessing (Contraction Hierarchies). If you don't like this, just disable it and also further fine-tune the included streets for car or probably better create a new profile for trucks - e.g. exclude service streets and tracks which should give you a further 30% boost. And as with any bidirectional algorithm you could easily implement a parallel search.