光电突触器件权重离散特性对图像识别性能的影响
Impact of Discrete Characteristics of Photoelectric Synaptic Devices on Image Recognition Performance
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摘要: 随着互联网和数字技术的快速发展, 各类数据爆炸式增长, 以图像识别为代表的任务亟须对海量数据高效分析和处理的手段, 从而推动人工智能技术的快速发展。现有的基于冯诺依曼架构的常规图像识别技术由于自身感、存、算分离的特点, 在运算速度和功耗方面受到极大的限制。为此, 近年来发展了一种非冯诺依曼架构的片上图像识别解决方案, 这种新型的基于人工突触的存算一体图像识别技术相比传统冯诺依曼架构的图像识别技术具有功耗更低、运算速度更快的优点。然而, 由于突触元件的设计和制造技术限制, 人工突触的电导往往是离散的, 导致该类新型图像识别技术的可部署权重值是分散的, 这意味着无法部署理想的神经网络权重, 从而降低了图像识别效果。为了解决这一问题, 基于Keras库设计了相关算法, 将连续的理想权重量化成离散权重, 以模拟实际器件的非理想特性。探讨了权重离散程度、权重的分布模式以及图像不同区域对神经网络在图像识别任务中准确率的影响。研究发现, 通过增加权重选项数, 即使用精度更高的器件, 可以有效减少权重非理想特性的影响; 权重离散特性对信息密度高的图像区域影响更大, 在资源受限时, 应优先考虑这些区域; 权重的各种分布模式在图像不同区域产生的效果各异, 每个子区域都有对应的最优分布。在不同子区域选择各自最优权重分布所组成的“综合分布模式”可以最有效地降低离散特性所带来的影响, 但相比单一的分布模式, 性能提升有限。探究结果揭示了图像各区域的不同权重量化级别对识别性能的具体影响, 为优化基于人工突触的图像识别系统提供了有价值的参考。Abstract: With the rapid development of the internet and digital technology, various types of data are being generated explosively. Image recognition tasks urgently require efficient analysis and processing techniques, thus driving the rapid development of artificial intelligence technology. The existing conventional image recognition technology based on the von Neumann architecture is significantly limited in computation speed and power consumption due to the separation of sensing, storage, and computation units. To address this issue, a novel on-chip image recognition solution with a non-von Neumann architecture has been developed. This new image recognition technology, based on in-memory computing with artificial synapses, offers lower power consumption and faster processing speeds compared to traditional von Neumann architecture-based image recognition technology. However, due to limitations in the design and manufacturing technology of synaptic components, the conductance of artificial synapses is often discrete, leading to scattered weight values in such new image recognition technologies. This means that it is impossible to deploy ideal neural network weights, thereby reducing the effectiveness of image recognition. To solve this problem, this study designed related algorithms using the Keras library, quantizing continuous ideal weights into discrete weights to simulate the non-ideal characteristics of actual devices. The study explored the effects of weight dispersion, distribution patterns of weights, and different image regions on the accuracy of neural networks in image recognition tasks. The research found that increasing the number of weight options, i.e., using higher precision devices, can effectively reduce the impact of non-ideal weight characteristics; the discrete nature of weights has a greater impact on image regions with high information density, and these areas should be prioritized when resources constrains; different distribution patterns of weights produce varying effects in different image regions, and each sub-region has its optimal distribution. Using an "integrated distribution model" composed of the optimal weight distributions for different sub-regions can most effectively reduce the impacts brought by discrete characteristics, although the performance improvement is limited compared to a single distribution pattern. The results reveal the specific impacts of different weight quantization levels in various image areas on recognition performance, providing valuable references for optimizing image recognition systems based on artificial synapses.
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