The GASPI API: A Failure Tolerant PGAS API for Asynchronous Dataflow on Heterogeneous Architectures

Abstract

The Global Address Space Programming Interface (GASPI) is a Partitioned Global Address Space (PGAS) API specification. The GASPI API specification is focused on three key objectives: scalability, flexibility and fault tolerance. It offers a small, yet powerful API composed of synchronization primitives, synchronous and asynchronous collectives, fine-grained control over one-sided read and write communication primitives, global atomics, passive receives, communication groups and communication queues. GASPI has been designed for one-sided RDMA-driven communication in a PGAS environment. As such, GASPI aims to initiate a paradigm shift from bulk-synchronous two-sided communication patterns towards an asynchronous communication and execution model. In order to achieve its much improved scaling behaviour GASPI leverages request based asynchronous dataflow with remote completion. In GASPI request based remote completion indicates that the operation has completed at the target window. The target hence can (on a per request basis) establish whether a one sided operation is complete at the target. A correspondingly implemented fine-grain asynchronous dataflow model can achieve a largely improved scaling behaviour relative to MPI.