The Small Solution Hypothesis for MAPF on Strongly Connected Directed Graphs Is True
This resolves a long-standing open problem in computational complexity for directed multi-agent pathfinding, providing a foundational result for the field.
The paper proves the short solution hypothesis for multi-agent pathfinding on strongly connected directed graphs, establishing that the problem is in NP, even with synchronous rotations.
The determination of the computational complexity of multi-agent pathfinding on directed graphs (diMAPF) has been an open research problem for many years. While diMAPF has been shown to be polynomial for some special cases, only recently, it has been established that the problem is NP-hard in general. Further, it has been proved that diMAPF will be in NP if the short solution hypothesis for strongly connected directed graphs is correct. In this paper, it is shown that this hypothesis is indeed true, even when one allows for synchronous rotations.