HPIM-NoC: A Priori-Knowledge-Based Optimization Framework for Heterogeneous PIM-Based NoCs

Network-on-Chip (NoC) accelerators with heterogeneous Processing-in-Memory (PIM) cores achieve superior performance than homogeneous ones for neural networks. Dedicated simulators and architecture search frameworks are pivotal for obtaining performance, power, and area (PPA) metrics, as well as guiding the design process. However, existing simulators are primarily designed for homogeneous NoC and lack support for simulating heterogeneous PIM-based NoC architectures. Besides, current search frameworks for heterogeneous NoC architectures only focus on workload allocation and mapping strategies, failing to explore heterogeneous PIM configurations in a larger design space. In this work, we propose HPIM-NoC, a joint simulation and search framework for heterogeneous PIM-based NoC architectures. HPIM-NoC not only supports the simulation of heterogeneous PIM cores, but also provides more accurate latency results by introducing NoC transmission delays and pipelines in co-simulation. HPIM-NoC implements a three-stage heterogeneous search process based on priori knowledge and employs a specific simulated annealing algorithm tailored for heterogeneous architecture search. The search process is accelerated by precomputing core PPA metrics and reducing NoC simulation frequency. In addition, the framework integrates a customized layout algorithm to optimize the placement of heterogeneous NoC, minimizing communication latency and overall area. Experimental results on various neural networks demonstrate that HPIM-NoC can quickly find near-optimal configurations within a limited time. The proposed acceleration method reduces the search time of HPIM-NoC by $2.12 \times$, $2.17 \times$, and $2.96 \times$, respectively. Compared to homogeneous architectures, the Fusions of Metrics (FoMs) of heterogeneous PIM-based NoC architectures found by HPIM-NoC are reduced by $\mathbf{1. 1 8 \%, ~} \mathbf{1 6. 9 4 \%}$, and $\mathbf{3 7. 4 1 \%}$ for ResNet-18 under three settings, respectively.