アナログインメモリ計算回路の非理想的特性を取り込む ODE ベース学習手法を開発~実用規模の学習に成功~

2025-11-05 千葉工業大学

Web要約 の発言:
千葉工業大学・東京大学・京都大学などの共同研究チームは、アナログインメモリ計算(AIMC)回路の非理想的特性を取り込み、実用規模AIを高効率で学習できる新手法を開発した。回路動作を常微分方程式(ODE)として記述し学習モデルに組み込むことで、ハードウェアとソフトウェアの挙動差を解消。さらに独自の離散化手法「Differentiable Spike-Time Discretization(DSTD)」により学習効率を約1000倍向上させ、8層CNNの学習に成功した。結果、従来は性能低下要因とされたアナログ回路の非線形性が、むしろ学習性能を高める可能性を示した。成果はAdvanced Intelligent Systems誌に掲載。

<関連情報>

アナログインメモリコンピューティング回路における非理想性の活用:ニューロモルフィックシステムのための物理モデリングアプローチ Harnessing Nonidealities in Analog In-Memory Computing Circuits: A Physical Modeling Approach for Neuromorphic Systems

Yusuke Sakemi, Yuji Okamoto, Takashi Morie, Sou Nobukawa, Takeo Hosomi, Kazuyuki Aihara
Advanced Intelligent Systems  Published: 18 August 2025
DOI:https://doi.org/10.1002/aisy.202500351

Abstract

Large-scale deep learning models are increasingly constrained by their immense energy consumption, which limits their scalability and applicability for edge intelligence. In-memory computing (IMC) offers a promising solution by addressing the von Neumann bottleneck inherent in traditional deep learning accelerators, significantly reducing energy consumption. However, the analog nature of IMC introduces hardware nonidealities that degrade model performance and reliability. This article presents a novel approach to directly train physical models of IMC, formulated as ordinary differential equation (ODE)-based physical neural networks (PNNs). To enable the training of large-scale networks, a technique called differentiable spike-time discretization is proposed, which reduces the computational cost of ODE-based PNNs by up to 20 times in speed and 100 times in memory. Such large-scale networks enhance learning performance by exploiting hardware nonidealities on the CIFAR-10 dataset. The proposed bottom-up methodology is validated through post-layout SPICE simulations on the IMC circuit with nonideal characteristics using the sky130 process. The proposed PNN approach reduces the discrepancy between model behavior and circuit dynamics by at least an order of magnitude. This work paves the way for leveraging nonideal physical devices, such as nonvolatile resistive memories, for energy-efficient deep learning applications.

1602ソフトウェア工学
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