S. Ali Mirsoleimani
Jaap van den Herik
Leiden University Niels Bohrweg 1 and Nikhef Theory Group, Netherlands
Leiden University Niels Bohrweg 1, Netherlands
Nikhef Theory Group, Netherlands
MCTS, Virtual Loss, Tree Parallelization, Search Overhead, Exploitation-exploration Trade-off.
Informatics in Control, Automation and Robotics
Intelligent Control Systems and Optimization
Knowledge Discovery and Information Retrieval
Planning and Scheduling
Simulation and Modeling
Monte Carlo tree search algorithms, such as UCT, select the best-root-child as a result of an iterative search
process consistent with path dependency. Recent work has provided parallel methods that make the search
process faster. However, these methods violate the path-dependent nature of the sequential UCT process.
Here, a more rapid search thus results in a higher search overhead. The cost thereof is a lower time efficiency.
The concept of virtual loss is proposed to compensate for this cost. In this paper, we study the role of virtual
loss. Therefore, we conduct an empirical analysis of two methods for lock-free tree parallelization, viz. one
without virtual loss and one with the virtual loss. We use the UCT algorithm in the High Energy Physics
domain. In particular, we methodologically evaluate the performance of the both methods for a broad set
of configurations regarding search overhead and time efficiency. The results show that using virtual loss for
lock-free tree paralleliza
tion still degrades the performance of the algorithm. Contrary to what we aimed at.