  With the expansion of the scale of robotics applications, the multi-goal
multi-agent pathfinding (MG-MAPF) problem began to gain widespread attention.
This problem requires each agent to visit pre-assigned multiple goal points at
least once without conflict. Some previous methods have been proposed to solve
the MG-MAPF problem based on Decoupling the goal Vertex visiting order search
and the Single-agent pathfinding (DVS). However, this paper demonstrates that
the methods based on DVS cannot always obtain the optimal solution. To obtain
the optimal result, we propose the Multi-Goal Conflict-Based Search (MGCBS),
which is based on Decoupling the goal Safe interval visiting order search and
the Single-agent pathfinding (DSS). Additionally, we present the
Time-Interval-Space Forest (TIS Forest) to enhance the efficiency of MGCBS by
maintaining the shortest paths from any start point at any start time step to
each safe interval at the goal points. The experiment demonstrates that our
method can consistently obtain optimal results and execute up to 7 times faster
than the state-of-the-art method in our evaluation.
