Title
Parallel Monte Carlo Tree Search from Multi-core to Many-core Processors
Abstract
In recent years there has been much interest in the MCTS algorithm, a new, adaptive, randomized optimization algorithm. In fields as diverse as Artificial Intelligence, Operations Research, and High Energy Physics, research has established that MCTS can find good solutions without domain dependent heuristics. However, practice shows that reaching high performance on large parallel machines is not so successful as expected. So far, the reasons are not well understood. This paper investigates the scalability of two popular parallelization approaches (tree parallelization and root parallelization) of the MCTS algorithm, using the Intel Xeon Phi highly multi-threaded shared-memory system. Moreover, we compare the results on a Xeon CPU and a Xeon Phi to understand the scalability of the parallel MCTS algorithms, and to understand their absolute performance. We find that tree parallelization can achieve near perfect speedup for up to 16 threads on the Xeon CPU and up to 64 threads on the Xeon Phi. For root parallelization we find that the effect of locks is small. Moreover, we establish the overall parallel speedup of the two parallelization methods of the MCTS algorithm is fundamentally limited on the Xeon Phi for games such as Hex or Go. The limiting factor is not, as might be expected, the parallel algorithm, or its implementation, but the high level of sequential calculations in each thread, for which no vectorization method is known.
Year
DOI
Venue
2015
10.1109/Trustcom.2015.615
TrustCom/BigDataSE/ISPA
Keywords
Field
DocType
parallel Monte Carlo tree search,multicore processors,many-core processors,adaptive randomized optimization algorithm,domain dependent heuristics,parallel machines,parallelization approach,Intel Xeon Phi,multithreaded shared-memory system,Xeon CPU,parallel MCTS algorithms,tree parallelization,root parallelization,Hex or Go,parallel algorithm
Monte Carlo tree search,Parallel algorithm,Computer science,Xeon Phi,Parallel computing,Xeon,Multi-core processor,Automatic parallelization,Speedup,Scalability
Conference
Volume
ISSN
Citations 
3
2324-9013
0
PageRank 
References 
Authors
0.34
13
4
Name
Order
Citations
PageRank
Sayyed Ali Mirsoleimani191.17
Aske Plaat252472.18
H. Jaap van den Herik3861137.51
Jos Vermaseren454.15