Taming Heterogeneity by Segregation -- The DEEP and DEEP-ER take on Heterogeneous Cluster Architectures

On the way to explore the path to Exascale, the DEEP/-ER projects take a radically different approach on heterogeneity. Instead of combining different computing elements within single nodes DEEP/-ER's Cluster-Booster concept integrates multi-core processors in a standard Cluster while combining many-core processors in a separate cluster of accelerators, the so-called Booster. For this, DEEP's Booster consists solely of Intel Xeon Phi processors interconnected by the EXTOLL network.The talk will not only share insights on the challenges of the hardware integration in a most energy efficient way but also discuss the strong requirements the architecture poses on the corresponding programming model. While it turns out that MPI provides all the low-level semantics required to utilize the Cluster-Booster system, the project uses an OmpSs abstraction layer in order to support software developers to adapt their applications to the heterogeneous hardware. The ultimate goal is to reduce the burden on the application developers. To this end DEEP/-ER provides a well-accustomed programming environment that saves application developers from some of the tedious and often costly code modernisation work. Confining this work to code-annotation as proposed by DEEP/-ER is a major advancement.The presentation is completed by final results of the DEEP project that is finalized by end of August 2015