基于自适应时间步脉冲神经网络的高效图像分类

李千鹏; 贾顺程; 张铁林; 陈亮

doi:10.16383/j.aas.c230656

基于自适应时间步脉冲神经网络的高效图像分类

doi: 10.16383/j.aas.c230656 cstr: 32138.14.j.aas.c230656

李千鹏^{1, 2,},
贾顺程^{1, 2,},
张铁林^{1, 2, 3,},
陈亮^{1, 2,}

1.
中国科学院自动化研究所北京 100190
2.
中国科学院大学人工智能学院北京 101408
3.
中国科学院脑科学与智能技术卓越创新中心上海 200031

基金项目: 国家重点研发计划(2021ZD0200300)资助

详细信息

作者简介:
李千鹏：中国科学院自动化研究所硕士研究生. 主要研究方向为类脑智能, 类脑处理器. E-mail: liqianpeng2021@ia.ac.cn

贾顺程：中国科学院自动化研究所博士研究生. 主要研究方向为类脑脉冲神经网络模型与学习算法. E-mail: jiashuncheng2020@ia.ac.cn

张铁林：中国科学院脑科学与智能技术卓越创新中心研究员. 主要研究方向为类脑计算. E-mail: zhangtielin@ion.ac.cn

陈亮：中国科学院自动化研究所副研究员. 主要研究方向为计算机架构与集成电路设计, 类脑计算. 本文通信作者. E-mail: liang.chen@ia.ac.cn

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出版历程
- 收稿日期: 2023-10-25
- 录用日期: 2024-03-15
- 网络出版日期: 2024-07-31
- 刊出日期: 2024-09-19

Adaptive Timestep Improved Spiking Neural Network for Efficient Image Classification

LI Qian-Peng^{1, 2
,},
JIA Shun-Cheng^{1, 2
,},
ZHANG Tie-Lin^{1, 2, 3
,},
CHEN Liang^{1, 2
,}

1.
Institute of Automation, Chinese Academy of Sciences, Beijing 100190
2.
School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing 101408
3.
Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031

Funds: Supported by National Key Research and Development Program of China (2021ZD0200300)

More Information

Author Bio:
LI Qian-Peng　Master student at the Institute of Automation, Chinese Academy of Sciences. His research interest covers brain-inspired intelligence and brain-inspired processor

JIA Shun-Cheng　Ph.D. candidate at the Institute of Automation, Chinese Academy of Sciences. His research interest covers brain-inspired spiking neural network model and learning algorithm

ZHANG Tie-Lin Researcher at the Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences. His main research interest is brain-inspired computing

CHEN Liang　Associate researcher at the Institute of Automation, Chinese Academy of Sciences. His research interest covers computer architecture and integrated circuit design and brain-inspired computing. Corresponding author of this paper

摘要

摘要: 脉冲神经网络(Spiking neural network, SNN)由于具有相对人工神经网络(Artifcial neural network, ANN)更低的计算能耗而受到广泛关注. 然而, 现有SNN大多基于同步计算模式且往往采用多时间步的方式来模拟动态的信息整合过程, 因此带来了推理延迟增大和计算能耗增高等问题, 使其在边缘智能设备上的高效运行大打折扣. 针对这个问题, 本文提出一种自适应时间步脉冲神经网络(Adaptive timestep improved spiking neural network, ATSNN)算法. 该算法可以根据不同样本特征自适应选择合适的推理时间步, 并通过设计一个时间依赖的新型损失函数来约束不同计算时间步的重要性. 与此同时, 针对上述ATSNN特点设计一款低能耗脉冲神经网络加速器, 支持ATSNN算法在VGG和ResNet等成熟框架上的应用部署. 在CIFAR10、CIFAR100、CIFAR10-DVS等标准数据集上软硬件实验结果显示, 与当前固定时间步的SNN算法相比, ATSNN算法的精度基本不下降, 并且推理延迟减少36.7% ~ 58.7%, 计算复杂度减少33.0% ~ 57.0%. 在硬件模拟器上的运行结果显示, ATSNN的计算能耗仅为GPU RTX 3090Ti的4.43% ~ 7.88%. 显示出脑启发神经形态软硬件的巨大优势.
- 脉冲神经网络 /
- 低功耗推理 /
- 高效训练 /
- 低延迟
Abstract: Spiking neural network (SNN) has received broad attention for its relatively lower computational energy consumption compared to artificial neural network (ANN). However, most conventional SNNs use a synchronous computation paradigm, whereby multiple timesteps are commonly used to simulate the dynamic process of information integration, resulting in some problems such as extended inference delay and increased computational energy consumption, which lead to a serious efficiency discount during the realistic application of edge intelligent devices. In this paper, we propose an adaptive timestep improved spiking neural network (ATSNN) algorithm, which can automatically choose a proper inference timestep based on different features of input samples, and regulate the importance of different timesteps by designing an innovative time-dependent loss function. Besides, a low energy consumption SNN accelerator is designed based on the characteristics of ATSNN mentioned above to support applications and deployments of ATSNN algorithm on some mature frameworks (such as VGG and ResNet). The results of software and hardware experiments on standard datasets such as CIFAR10, CIFAR100, and CIFAR10-DVS show that, compared to conventional SNN algorithms using static timesteps, the ATSNN algorithm can reach a comparable accuracy but with a decreased inference delay (around 36.7% ~ 58.7%) and reduced computational complexity (around 33.0% ~ 57.0%). Furthermore, the running results on the hardware simulator indicate that the computational energy consumption of ATSNN is only around 4.43% ~ 7.88% of GPU RTX 3090Ti. It shows great advantages of brain-inspired neuromorphic hardware and software.
- Spiking neural network (SNN) /
- low power consumption inference /
- efficient training /
- low latency

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图 1 ATSNN结构及训练和动态时间推理流程图

Fig. 1 ATSNN structure and training and dynamic time inference flow chart

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图 2 加速器架构((a)常规加速器; (b) DTSNN的加速器; (c)本文加速器)

Fig. 2 Accelerator architecture ((a) Conventional accelerator; (b) Accelerator of DTSNN; (c) Our accelerator)

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图 3 不同平均推理时间步时的准确率

Fig. 3 Accuracy at different average inference timesteps

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图 4 固定时间步时使用三种损失函数的准确率

Fig. 4 Accuracy by using three loss functions at fixed timestep

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图 5 超参数对准确率的影响

Fig. 5 The effect of hyperparameters on accuracy

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图 6 超参数对时间步的影响

Fig. 6 The effect of hyperparameters on timestep

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图 7 $ \tau_{CL}\ne1 $和$ \tau_{CL} =1$时的性能对比

Fig. 7 Performance comparison between $ \tau_{CL}\ne1 $ and $ \tau_{CL}= 1 $

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表 1 SNN、DTSNN和ATSNN在时间步、准确率和复杂度的对比

Table 1 Comparison of SNN, DTSNN and ATSNN in timestep, accuracy and complexity

网络结构	算法	CIFAR10			CIFAR100			CIFAR10-DVS
网络结构	算法	时间步	准确率(%)	复杂度	时间步	准确率(%)	复杂度	时间步	准确率(%)	复杂度
VGG16	SNN	4.00	91.35	1.00	4.00	66.99	1.00	10.00	72.60	1.00
	DTSNN	2.53 (4)	91.13	0.79	3.58 (4)	69.68	0.96	5.70 (10)	73.30	0.56
	ATSNN	2.19 (4)	91.61	0.67	2.49 (4)	70.05	0.63	4.13 (10)	73.00	0.43
ResNet19	SNN	4.00	91.86	1.00	4.00	67.22	1.00	10.00	70.00	1.00
	DTSNN	2.52 (4)	91.51	0.88	3.54 (4)	67.58	1.02	6.95 (10)	70.50	0.94
	ATSNN	2.00 (4)	91.84	0.67	2.53 (4)	70.64	0.64	5.57 (10)	69.50	0.63

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表 2 每个时间步的相对计算复杂度及网络性能

Table 2 Relative computational complexity per timestep and network performance

数据集	T1	T2	T3	T4	T5	$\tilde{T}$ (%)	$\Delta ACC$ (%)
ImageNet-100	0.998	1.009	1.009	1.010	1.003	68.49	0.90
N-Caltech-101	0.959	0.977	0.978	0.959	0.989	68.32	0.45

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表 3 加速器与GPU关于FPS、耗能对比

Table 3 Comparison of FPS and energy consumption between accelerator and GPU

网络结构	数据集	GPU		本文加速器
网络结构	数据集	FPS	耗能(J)	FPS	耗能(J)
VGG16	CIFAR10	215	6814	248	537.6 (7.88%)
VGG16	CIFAR100	200	7499	228	543.6 (7.24%)
ResNet19	CIFAR10	215	11088	212	606.1 (5.46%)
ResNet19	CIFAR100	172	13914	180	617.2 (4.43%)

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表 4 默认超参数的性能

Table 4 Performance with default hyperparameters

数据集	网络结构	时间步	准确率(%)
CIFAR10	ResNet19	1.897 (4)	91.77
CIFAR10	VGG16	2.183 (4)	91.57
CIFAR100	ResNet19	2.501 (4)	70.46
CIFAR100	VGG16	2.642 (4)	69.58

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表 5 ATSNN消融实验

Table 5 Ablation experiment of ATSNN

数据集	输出层神经元	损失函数	输出表征	T1	T2	T3	T4
CIFAR10				34.43	89.39	90.82	91.86
	√			47.26	89.85	90.52	91.38
		√		85.68	88.78	90.39	91.28
	√	√		86.93	89.96	91.63	91.79
	√	√	√	86.93	90.14	91.39	91.86
CIFAR100				27.13	56.68	62.53	67.22
	√			30.38	57.19	63.37	67.70
		√		52.69	63.80	67.29	69.61
	√	√		53.47	64.35	67.53	69.90
	√	√	√	53.47	65.23	68.17	70.25

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表 6 ATSNN与低延迟算法的对比

Table 6 Comparison between ATSNN and low-latency algorithms

数据集	算法	算法类型	网络结构	时间步	准确率 (%)
CIFAR10	Conversion^[11]	ANN转SNN	VGG16	8	90.96
	STDB^[33]	转换+训练	VGG16	5	91.41
	EfficientLIF-Net^[10]	直接训练	VGG16	5	90.30
	DTSNN^[19]	直接训练	VGG16	2.53 (4)	91.13
	本文	直接训练	VGG16	2.56 (10)	92.09
	STBP-tdBN^[14]	直接训练	ResNet19	6	93.16
	DTSNN^[19]	直接训练	ResNet19	2.51 (4)	91.51
	本文	直接训练	ResNet19	2.71 (10)	92.38
CIFAR100	STDB^[33]	转换+训练	VGG16	5	66.46
	Diet-SNN^[15]	直接训练	VGG16	5	69.67
	Real Spike^[34]	直接训练	VGG16	5	70.62
	RecDis-SNN^[35]	直接训练	VGG16	5	69.88
	本文	直接训练	VGG16	3.86 (10)	71.37
	DTSNN^[19]	直接训练	ResNet19	3.54 (4)	67.58
	本文	直接训练	ResNet19	2.53 (10)	70.64
CIFAR10-DVS	STBP-tdBN^[14]	直接训练	ResNet19	6	67.80
	DTSNN^[19]	直接训练	ResNet19	6.95 (10)	70.50
	本文	直接训练	ResNet19	5.57 (10)	69.50
ImageNet-100	EfficientLIF-Net^[10]	直接训练	ResNet19	5	79.44
	LocalZO^[36]	直接训练	SEW-ResNet34	4	81.56
	本文	直接训练	ResNet19	1.76 (5)	81.96
TinyImageNet	EfficientLIF-Net^[10]	直接训练	ResNet19	5	55.44
	DTSNN^[19]	直接训练	ResNet19	3.71 (5)	57.18
	本文	直接训练	ResNet19	2.47 (5)	57.61
N-Caltech-101	MC-SNN^[37]	直接训练	VGG16	20	81.24
	DTSNN^[19]	直接训练	VGG16	3.21 (10)	82.26
	本文	直接训练	VGG16	2.19 (10)	82.63
	NDA^[30]	直接训练	ResNet19	10	78.60
	本文	直接训练	ResNet19	2.56 (10)	80.56

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