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Universal Numbers Library: design and implementation of a high-performance reproducible number systems library (2012.11011v1)

Published 20 Dec 2020 in cs.CE and cs.MS

Abstract: With the proliferation of embedded systems requiring intelligent behavior, custom number systems to optimize performance per Watt of the entire system become essential components for successful commercial products. We present the Universal Number Library, a high-performance number systems library that includes arbitrary integer, decimal, fixed-point, floating-point, and introduces two tapered floating-point types, posit and valid, that support reproducible arithmetic computation in arbitrary concurrency environments. We discuss the design of the Universal library as a run-time for application development, and as a platform for application-driven hardware validation. The library implementation is described, and examples are provided to show educational examples to elucidate the number system properties, and how specialization is used to yield very high-performance emulation on existing x86, ARM, and POWER processors. We will highlight the integration of the library in larger application environments in computational science and engineering to enable multi-precision and adaptive precision algorithms to improve performance and efficiency of large scale and real-time applications. We will demonstrate the integration of the Universal library into a high-performance reproducible linear algebra run-time. We will conclude with the roadmap of additional functionality of the library as we are targeting new application domains, such as Software Defined Radio, instrumentation, sensor fusion, and model-predictive control.

Citations (11)

Summary

  • The paper introduces the posit number system to overcome IEEE floating-point limitations by enabling more precise, reproducible arithmetic.
  • It details a header-only, modern C++ implementation that supports multi-precision configurations and hardware verification across platforms.
  • Empirical results demonstrate improved convergence, error reduction, and energy efficiency in applications like sensor fusion and model-predictive control.

Universal Numbers Library: Design and Implementation

The "Universal Numbers Library" paper addresses the increasing demand for intelligent embedded systems requiring optimized number systems that enhance performance and energy efficiency. With traditional IEEE floating point facing limitations due to rounding rules that disrupt algebraic laws, this paper presents the Universal Number Library—an innovative library designed to offer high-performance, reproducible number systems.

Overview

The core of the Universal Number Library is its introduction of the posit number system, alongside various numerical formats like arbitrary integer, decimal, and traditional floating point. Posits, as highlighted, provide improved information density over IEEE counterparts, making them apt for high-performance computation environments. The library's implementation and its application within computational science and engineering are detailed, promoting multi-precision and adaptive precision algorithms to advance performance metrics.

Posit Number System

Posits, stemming from John Gustafson's work, offer a compelling alternative to IEEE floats with larger dynamic ranges and higher accuracy for a given number of bits. The library includes highly parameterizable configurations, enabling a tailored approach to specific application requirements. The detailed discussion on posits illustrates their unique structure, including sign, regime, exponent, and fraction components, facilitating nuanced handling of mathematical operations.

The posit system's ability to uniquely manage rounding and provide reproducibility in arithmetic operations sets it apart. This reproducibility is vital in environments with significant parallelism, where traditional floating-point systems may falter.

Library Implementation

Implemented in modern C++, the library is header-only and devoid of external dependencies, ensuring compatibility across platforms and compilers. By supporting hardware verification, it serves as a robust reference for custom implementations, which adds considerable value in varied computational contexts.

Applications and Implications

The library's integration into tools like the Matrix Tensor Library and its facilitation of posits in environments such as TVM and G+Smo showcase its application range. These integrations underscore posits' potential to enhance convergence in numerical solutions and provide higher error reduction in iterative solvers compared to traditional floating-point systems.

The empirical results delineated—demonstrating faster convergence and superior error preservation—reflect the practical benefits posits bring to complex computations. Moreover, the implications extend into real-world use cases such as software-defined radio, sensor fusion, and model-predictive control.

Future Directions

The research sets the stage for further exploration into multi-precision algorithms, particularly in reproducing results in chaotic systems or those with highly variable dynamic ranges. Implementing a universal math library that adheres to exact rounding methods in posits remains an active research area poised to address current limitations.

In conclusion, the Universal Numbers Library signifies a substantive evolution in numerical libraries, addressing inherent constraints found in conventional floating-point approaches. By broadening the landscape of numerical computation through posits and associated systems, this work lays the groundwork for future advancements in both theoretical exploration and practical application domains, especially where reproducibility and precision are critical.