  In this paper, we present a new algorithm for parallel Monte Carlo tree
search (MCTS). It is based on the pipeline pattern and allows flexible
management of the control flow of the operations in parallel MCTS. The pipeline
pattern provides for the first structured parallel programming approach to
MCTS. Moreover, we propose a new lock-free tree data structure for parallel
MCTS which removes synchronization overhead. The Pipeline Pattern for Parallel
MCTS algorithm (called 3PMCTS), scales very well to higher numbers of cores
when compared to the existing methods.
