CAREER: General-Purpose Stochastic Computing for Ultra-Low-Power Hardware Devices

技术趋势正朝着超低功耗计算的未来发展，届时一切事物（无论是手指上的戒指，还是体内的植入物）都将具备某种形式的智能处理能力。然而，这样的未来无法通过今天的平板电脑和智能手机设备中使用的传统处理器来实现。虽然典型的计算机运行功率预算为10 -100瓦，但超低功率设备需要能够低至10毫瓦。尽管功耗低了几个数量级，但这些设备需要具有相同的计算能力和通用可编程性，以支持数据分析、机器学习和无线通信等复杂任务，这些任务对这些应用程序至关重要。换句话说，即使有可能使处理器硬件超低功耗，如果软件开发人员无法编写可以在这些设备上运行的高效程序，这些设备也将无法使用。该提案提出了随机计算（SC）的案例，这是一种设计超低功耗系统的非常规方法。SC不是以二进制读写数据，而是以一元格式读写数据，其中数据被编码为概率而不是标准数字。这种非常规的计算方式允许SC用比二进制小几个数量级的电路来执行计算。例如，在SC中，一个乘法器电路从100个逻辑门缩小到一个逻辑门。尽管很有前途，但由于几个原因，使用SC构建处理器并不是一件简单的事情。首先，普遍缺乏可公开用于设计、模拟和比较SC电路的标准工具链。其次，之前的SC工作大多是个案分析，提出的电路只适用于特定的应用程序，缺乏足够的可编程性，软件开发人员无法编写有用的程序。该项目的技术目标是降低非专业开发人员考虑在其系统中采用SC的门槛。PIs的目标是开发和标准化一个名为UnarySim的开源框架，用于快速设计和评估SC系统。利用pi在构建高效SC电路方面的初步工作，该项目将最终设计出第一个通用的可编程SC处理器，该处理器可以支持各种超低功耗应用。如果提议的研究成功，它可以帮助增殖萌芽中的SC社区，并使SC成为技术行业的一个实用（和有竞争力的）选择。该提案的总体目标是实现超低功耗计算的潜力，使其能够以10美分的成本（和尺寸）执行前所未有的计算任务。这可以为重要的新应用打开大门，如智能起搏器、可穿戴设备、增强现实和精准农业等。从这项研究中获得的见解将在科学场所公开传播，并纳入课程，向年轻学生传授节能原则及其对更广泛社区的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Technology trends are moving towards a future of ultra-low-power computing where everything (whether it be a ring on a finger or even an implant in the body) becomes capable of some form of smart processing. However, such a future cannot be realized with the traditional processors used in today's tablets and smartphone devices. While typical computers operate at power budgets of 10s-100s of watts, ultra-low-power devices would need to be able to operate at as low as 10s of milliwatts. And despite orders of magnitude less power, such devices would need to have the same compute capabilities and general programmability to support complex tasks such as data analytics, machine learning and wireless communication that are essential for these applications. In other words, even if it becomes possible to make the processor hardware ultra-low-power, these devices would be unusable if software developers are not able to write efficient programs that can run on these devices. This proposal makes the case for stochastic computing (SC), an unconventional approach for designing ultra-low-power systems. Instead of reading and writing data in binary, SC reads and writes in unary, where data is encoded as probabilities instead of standard digital numbers. This unconventional computing style allows SC to perform computations with circuits that are orders of magnitude smaller than their binary counterparts. For example, a multiplier circuit shrinks from 100s of logic gates down to a single logic gate in SC. Though promising, building processors using SC is no simple feat for a couple of reasons. First, there is a general lack of standard toolchains publicly available for designing, simulating and comparing SC circuits. Second, prior SC works are mostly case-by-case, proposing circuits that only work for specific applications and lack sufficient programmability for software developers to write useful programs.The technical goal of this project is to lower the barrier-to-entry for non-expert developers to consider adopting SC in their systems. The PIs aim to develop and standardize an open-sourced framework, named UnarySim, for rapidly designing and evaluating SC systems. Leveraging the PIs' preliminary work on building efficient SC circuits, the project will culminate in the design of the first general-purpose, programmable SC processor that can support a variety of ultra-low-power applications. If the proposed research is successful, it can help proliferate the budding SC community and make SC a practical (and competitive) option in the tech industry. The broad goal of this proposal is to realize the potential of ultra-low-power computing, making it possible to perform unprecedented computing tasks at the cost (and size) of a dime. This can open the door for important new applications such as smart pacemakers, wearables, augmented reality and precision agriculture, to name a few. The insights gained from this research will be publicly disseminated in scientific venues and integrated into curricula to teach young students about power-saving principles and their impact on the broader community.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.