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Double-precision FPUs in High-Performance Computing: an Embarrassment of Riches? (1810.09330v3)

Published 22 Oct 2018 in cs.DC

Abstract: Among the (uncontended) common wisdom in High-Performance Computing (HPC) is the applications' need for large amount of double-precision support in hardware. Hardware manufacturers, the TOP500 list, and (rarely revisited) legacy software have without doubt followed and contributed to this view. In this paper, we challenge that wisdom, and we do so by exhaustively comparing a large number of HPC proxy application on two processors: Intel's Knights Landing (KNL) and Knights Mill (KNM). Although similar, the KNM and KNL architecturally deviate at one important point: the silicon area devoted to double-precision arithmetic's. This fortunate discrepancy allows us to empirically quantify the performance impact in reducing the amount of hardware double-precision arithmetic. Our analysis shows that this common wisdom might not always be right. We find that the investigated HPC proxy applications do allow for a (significant) reduction in double-precision with little-to-no performance implications. With the advent of a failing of Moore's law, our results partially reinforce the view taken by modern industry (e.g. upcoming Fujitsu ARM64FX) to integrate hybrid-precision hardware units.

Citations (16)

Summary

  • The paper presents an empirical analysis comparing Intel’s KNL and KNM architectures, demonstrating that reduced double-precision support minimally affects performance.
  • It employs comprehensive benchmarking with ECP and RIKEN proxy applications across diverse scientific domains, ensuring thorough evaluation of hardware precision impacts.
  • The study underscores a shift towards hybrid-precision computing, advocating for future HPC designs that better balance precision allocation with emerging AI and efficiency demands.

Essay on "Double-precision FPUs in High-Performance Computing: an Embarrassment of Riches?"

The paper "Double-precision FPUs in High-Performance Computing: an Embarrassment of Riches?" by Jens Domke et al. provides a meticulous examination of the role and necessity of double-precision Floating Point Units (FPUs) in High-Performance Computing (HPC). The authors challenge an entrenched belief that applications within the HPC community necessitate substantial double-precision support, an assumption that has influenced hardware configuration by manufacturers, affected TOP500 rankings, and persisted in software design.

Methodology and Experimental Setup

The core of the research utilizes a comparative analysis between Intel's Knights Landing (KNL) and Knights Mill (KNM) processors. Despite their architectural similarities, a crucial distinction exists in the silicon area allocated for double-precision arithmetics. This distinction serves as a basis to empirically assess performance implications arising from variations in hardware double-precision allocation.

The experimental design revolves around comprehensive benchmarking using two sets of proxy applications: 12 from the Exascale Computing Project (ECP) and eight from the RIKEN R-CCS suite. These benchmarks span domains including bioscience, material science, and quantum simulations, offering a broad spectrum of HPC workloads for evaluation. Each application underwent rigorous configuration, tuning for optimal performance, and execution on both KNL and KNM platforms.

Key Findings

The findings revealed a diminished performance impact from reducing double-precision support across most benchmarks. More specifically, reduced double-precision support in the KNM architecture had negligible effects on performance for a wide array of applications. The analysis demonstrated that low compute efficiency, with most applications reaching less than 10% of theoretical peak \unit[]{flop/s}, underlined the limited necessity of pervasive double-precision units for many modern HPC applications.

The research further corroborated the trending shift within the industry towards hybrid-precision hardware units, driven by evolving market demands, especially from the AI domain. Importantly, applications such as deep learning workloads absorb substantial benefits from reduced precision computational capabilities, emphasizing architectural evolution away from traditional double-precision-centric designs.

Implications and Future Directions

These insights prompt a re-evaluation of architecture design conventions, particularly regarding precision allocations. The apparent over-provisioning of double-precision FPUs suggests the need for a diversified approach in processor design, aligning more closely with contemporary and foreseeable demands in scientific computing and AI.

From a practical standpoint, the paper advocates for a shift in performance metric emphasis from pure \unit[]{flop/s} to more pertinent metrics reflecting real-world workload characteristics. Such a shift in procurement considerations could guide the development of future HPC systems optimized for hybrid workloads, ensuring balanced resource allocation that aligns with diverse computational requirements.

Theoretically, the findings encourage further research into heterogeneous precision computation, which could lead to innovative optimization techniques across computing platforms. There remains a scope for exploring trade-offs in semiconductor usage and precision computing to achieve optimal performance and energy efficiency.

Conclusion

Overall, the paper presents a compelling case questioning the status quo of double-precision prevalence in HPC architectures, highlighting the potential benefits of adopting hybrid-precision computing solutions. As HPC continues to intertwine with AI, the consideration of such architectural shifts will be essential in crafting the next generation of computational tools, aligning with both empirical needs and energy sustainability.

The comprehensive analysis provided by Domke et al. underscores the necessity for an agile approach in adapting to the transformative demands of modern computing environments, ensuring that HPC infrastructures remain both relevant and effective in addressing the multifaceted challenges of future computation.

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