LWMPI: An MPI library for NoC‐based lightweight manycore processors with on‐chip memory constraints

Abstract

Lightweight manycore processors deliver high performance and energy efficiency by bundling hundreds of low-power cores, a distributed memory architecture with small local memories and Networks-on-Chip in a single die. However, the lack of rich and portable programming models for these processors makes software development a challenging task. Currently, two approaches are employed to address programmability in lightweight manycores: Operating Systems (OSes) and baremetal runtime libraries.The former provides portability but exposes complex Operating System (OS)-level programming interfaces to developers. The latter focuses on providing rich and high performance interfaces, which are vendor-specific and yield to non-portable software.In this work, we address these programmability and portability challenges by combining a rich OS with a well-known standard for parallel programming. We propose a portable and lightweight Message Passing Interface (MPI) library (LWMPI) designed from scratch to cope with restrictions and intricacies of lightweight manycores. We integrated LWMPI into Nanvix, an open-source distributed OS that runs on silicon lightweight manycores. The results obtained with a synthetic benchmark and a subset of the CAP Bench applications running on Kalray MPPA-256 unveil that LWMPI not only delivers a lightweight and richer programming interface but also presents good performance and scalability results.