Evaluation of an MPI-based Implementation of the Tascell Task-Parallel Language on Massively Parallel Systems

Tascell is a task parallel language that supports distributed memory environments. The conventional implementation of Tascell realizes inter-node communication with TCP/IP communication via Tascell servers. This implementation is suitable for dynamic addition of computation nodes and wide-area distributed environments. On the other hand, in supercomputer environments, TCP/IP may not be available for inter-node communication and there may be no appropriate places for deploying Tascell servers. In this study, we have developed a server-less implementation of Tascell that realizes inter-node communication with MPI communication in order to evaluate its performance on massively parallel systems. It performs well on four Xeon Phi coprocessors (with 456 workers) and the K computer; for instance, our 19-queens solver achieves a 4615-fold speedup relative to a serial implementation with 7168 workers on the K computer. Our server-less implementation realizes deadlock freedom, although it only requires the two-sided communication paradigm and the MPI_THREAD_FUNNELED support level. On Xeon Phi coprocessors, we compare our implementation with other implementations that employ TCP/IP or the MPI_THREAD_MULTIPLE support level.