Asynchronous one-sided communications and synchronizations for a clustered manycore processor

Clustered manycore architectures fitted with a Network-on-Chip (NoC) and scratchpad memories enable highly energy-efficient and time-predictable implementations. However, porting applications to such processors represents a programming challenge. Inspired by supercomputer one-sided communication libraries and by OpenCL async_work_group_copy primitives, we propose a simple programming layer for communication and synchronization on clustered manycore architectures. We discuss the design and implementation of this layer on the 2nd-generation Kalray MPPA processor, where it is available from both OpenCL and POSIX C/C++ multithreaded programming models. Our measurements show that it allows to reach up to 94% of the theoretical hardware throughput with a best-case latency round-trip of 2.2μs when operating at 500 MHz.