HPX: A Task Based Programming Model in a Global Address Space

Abstract

The significant increase in complexity of Exascale platforms due to energy-constrained, billion-way parallelism, with major changes to processor and memory architecture, requires new energy-efficient and resilient programming techniques that are portable across multiple future generations of machines. We believe that guaranteeing adequate scalability, programmability, performance portability, resilience, and energy efficiency requires a fundamentally new approach, combined with a transition path for existing scientific applications, to fully explore the rewards of todays and tomorrows systems. We present HPX -- a parallel runtime system which extends the C++11/14 standard to facilitate distributed operations, enable fine-grained constraint based parallelism, and support runtime adaptive resource management. This provides a widely accepted API enabling programmability, composability and performance portability of user applications. By employing a global address space, we seamlessly augment the standard to apply to a distributed case. We present HPX's architecture, design decisions, and results selected from a diverse set of application runs showing superior performance, scalability, and efficiency over conventional practice.