Monte-Carlo Tree Search Parallelisation for Computer Go

Parallelisation of computationally expensive algorithms, such as Monte-Carlo Tree Search (MCTS), has become increasingly important in order to increase algorithm performance by making use of commonplace parallel hardware. Oakfoam, an MCTS-based Computer Go player, was extended to support parallel processing on multi-core and cluster systems. This was done using tree parallelisation for multi-core systems and root parallelisation for cluster systems. Multi-core parallelisation scaled linearly on the tested hardware on 9x9 and 19x19 boards when using the virtual loss modification. Cluster parallelisation showed poor results on 9x9 boards, but scaled well on 19x19 boards, where it achieved a four-node ideal strength increase on eight nodes. Due to this work, Oakfoam is currently one of only two open-source MCTS-based Computer Go players with cluster parallelisation, and the only one using the Message Passing Interface (MPI) standard.