ESL-SNNs: An Evolutionary Structure Learning Strategy for Spiking Neural Networks
Jiangrong ShenQi XuJian K. LiuYueming WangGang PanHuajin Tang
Proposes a biologically inspired evolutionary structure learning framework that enables training spiking neural networks from scratch with dynamic synaptic pruning and regeneration, achieving high accuracy with only a fraction of full network connectivity to minimize memory and power consumption.
Spiking neural networks are brain-inspired artificial intelligence models designed for high energy efficiency, but expanding their depth to match modern AI performance causes substantial parameter redundancy. Traditional techniques rely on post-training pruning, which removes unnecessary connections only after dense training is complete. Consequently, these models still suffer from excessive computational cost and memory overhead throughout the training phase, hindering their deployment on resource-constrained embedded and neuromorphic hardware.
The article evaluates an evolutionary structure learning framework designed to train sparse spiking neural networks from scratch. Inspired by the dynamic rewiring and structural plasticity observed in biological brains, the framework aims to maintain a fixed, low connection density throughout both training and inference without inheriting weights from pre-trained dense models.
The researchers assessed the approach through empirical evaluations on multi-layer feedforward and deep convolutional spiking architectures. They initialized network connectivity as sparse random graphs and applied periodic connection pruning alongside dynamic regeneration rules—including momentum-based and gradient-based strategies—to explore the parameter space during training. Testing covered standard vision benchmarks, including static image datasets and neuromorphic dynamic vision sensor data, while measuring classification accuracy, parameter counts, and estimated energy consumption across GPU and TrueNorth neuromorphic platforms.
The key findings demonstrate that dynamic sparse training achieves high structural efficiency with minimal accuracy loss. On neuromorphic vision data, the sparse network reached 78.30% accuracy with only 10% connection density, exhibiting an accuracy drop of just 0.28% relative to dense models while outperforming several state-of-the-art architectures. In feedforward network tests, the model maintained 96.58% accuracy with roughly six times fewer connections than the fully connected baseline, while energy estimations showed that running the resulting sparse models on neuromorphic hardware provided approximately one order of magnitude higher energy efficiency compared to GPU implementations. Furthermore, pairing magnitude-based pruning with momentum-based growth proved most effective at discovering optimal network topologies.
These results show that resource-efficient training from scratch is viable for spiking neural networks, significantly lowering memory footprints and compute costs during training as well as inference. This capability facilitates on-chip training on embedded neuromorphic systems, reducing development time and operational energy expenditures without requiring costly dense pre-training.
Organizations developing edge AI and neuromorphic systems should consider adopting dynamic sparse learning frameworks to streamline model training pipelines and lower hardware power requirements. Before committing to large-scale operational deployment, engineering teams should conduct pilot implementations on physical neuromorphic embedded systems to validate real-world hardware latency and energy gains across domain-specific workloads.
Confidence in these findings is supported by consistent results across multiple architectures and standard benchmarks. However, readers should note that energy metrics were derived from theoretical estimations rather than direct physical hardware measurements, and evaluations focused primarily on visual classification tasks. Broader operational verification across diverse real-time tasks will help confirm generalizability.
- Paper: Rigging the Lottery: Making All Tickets Winners, Utku Evci et al. (2020). Introduces the RigL dynamic sparse training paradigm of periodic magnitude-based pruning and gradient-based connection regrowth during training from scratch, which ESL-SNNs adapts to spiking architectures.
- Paper: Surrogate Gradient Learning in Spiking Neural Networks: Bringing the Power of Gradient-based optimization to spiking neural networks, Emre O. Neftci et al. (2019). Establishes the foundational surrogate gradient framework necessary to differentiate through non-smooth spiking thresholds and compute the parameter gradients used for network rewiring.
- Paper: Spatio-Temporal Backpropagation for Training High-Performance Spiking Neural Networks, Yujie Wu et al. (2017). Formulates spatio-temporal backpropagation through time for deep spiking neural networks, providing the core gradient optimization mechanism ESL-SNNs relies on during sparse training.
- Paper: Deep Learning in Spiking Neural Networks, Amirhossein Tavanaei et al. (2018). Surveys foundational training methodologies and architectural design principles for deep spiking neural networks.
- Paper: Rethinking the Value of Network Pruning, Zhuang Liu et al. (2019). Demonstrates that training sparse architectures from scratch can match or exceed fine-tuning dense pre-trained models, providing key conceptual motivation for ESL-SNNs.
- Paper: SNIP: Single-shot Network Pruning based on Connection Sensitivity, Namhoon Lee et al. (2018). Provides foundational insights into single-shot connection pruning at initialization to avoid computationally expensive dense pre-training cycles.
- Paper: The Lottery Ticket Hypothesis: Finding Sparse, Trainable Neural Networks., Jonathan Frankle et al. (2019). Establishes the existence of sparse, trainable sub-networks at random initialization, inspiring dynamic rewiring methods that seek optimal sparse topologies.
- Paper: Learning both Weights and Connections for Efficient Neural Networks, Song Han et al. (2015). Introduces classical magnitude-based iterative pruning for neural networks, which ESL-SNNs integrates as its primary connection removal criterion.
- Paper: Resource-Efficient Neural Networks for Embedded Systems, Wolfgang Roth et al. (2024). Provides a comprehensive hardware-centric evaluation of neural network compression and structural sparsity on embedded devices and neuromorphic hardware.
- Paper: SpikingResformer: Bridging ResNet and Vision Transformer in Spiking Neural Networks, Xinyu Shi et al. (2024). Extends efficient spiking architectures into vision transformer and residual hybrid models, offering advanced topologies suitable for sparse dynamic learning.
- Paper: DepGraph: Towards Any Structural Pruning, Gongfan Fang et al. (2023). Develops dependency graph mapping to automate structural pruning across diverse neural architectures, generalizing beyond layer-by-layer rewiring.
