Section: New Results

The Mont-Blanc prototype: An Alternative Approach for HPC Systems

Participants : Brice Videau, Kevin Pouget, Jean-François Méhaut.

The evolution of High-Performance Computing (HPC) systems is driven by the need of reducing time-to-solution and increasing the resolution of models and problems being solved by a particular program. Important milestones from the HPC system performance perspective were achieved using commodity technology. Examples are the ASCI Red and the Roadrunner supercomputers, which broke the 1 TFLOPS and 1 PFLOPS barriers, respectively. These systems showed how commodity technology could be used to take the next step in HPC system architecture.

Driven by a much larger market, commodity components evolve faster than their special-purpose counterparts, eventually achieving the same performance and eventually surpassing or replacing them. For this reason, RISC processors displaced vector processors, and x86 displaced RISC.

Nowadays commodity is in the embedded / mobile processor segment. Mobile processors develop fast, and are still not at a point of diminishing performance improvements from new designs. Furthermore, they progressively incorporate the capabilities required for HPC.

The embedded market size and endless customer requirements allow for constant investments into innovative designs, and rapid testing and adoption of new technologies. For example, LPDDR memory technology was first introduced in the mobile domain and has recently been proposed as a memory solution for energy proportional servers.

The Mont-Blanc project aims at providing an alternative HPC system solution based on the current commodity technology: mobile chips. As a demonstrator of such an approach, the project designed, built, and set-up a 1080-node HPC cluster made of Samsung Exynos 5250 SoCs. The Mont-Blanc project established the following goals: to design and deploy a sufficiently large HPC prototype system based on the current mobile commodity technology; to port and optimize the software stack, and enable its use for HPC; to port and optimize a set of HPC applications to be run at this HPC system.

Comparing the Mont-Blanc prototype to a contemporary supercomputer, MareNostrum III, reveals that a single-socket Mont-Blanc node is 9x slower than a dual-socket MareNostrum III node, while saving up to 40% of energy. MPI parallel applications show a 3.5x slowdown when running with the same number of MPI ranks on both machines, while consuming 9% less energy on the Mont-Blanc prototype on average. When targeting the same execution time, the Mont-Blanc prototype offers 12.5% space savings.

This work was funded by the European Commission with the Mont-Blanc projects 8.3.1.1. This scientific result was presented at the SuperComputing Conference SC'2016 in Salt Lake City [31]. The paper was selected as a best paper finalist.