Hi all, where can I find more details on the computation of a round_trip path? I suppose by default it uses a bidirectional A* under the hood that is meant to solve the point-to-point shortest path problem though. Any details and eventually references to papers would be super helpful! 
Thanks,
Rossano
This is a tough topic and there is no paper we used to implement this. The shortest path approach contradicts a bit the “round trip” use case. We initially solved it via calculating alternative paths and going one forward and the alternative backward but a simple heuristic based on “points in a circle” resulted in faster response times and better results. See the topic in the issues: https://github.com/graphhopper/graphhopper/pulls?q=is%3Apr+round+trip+is%3Aclosed