Amortized Neural Optimization for Pre-Layout Signal Integrity Design Space Exploration using Differentiable Surrogates
基于可微代理的布局前信号完整性设计空间探索的摊销神经优化
Julian Withöft, Werner John, Emre Ecik, Ralf Brüning, Jürgen Götze
AI总结 提出摊销神经优化(ANO)框架,利用可微神经网络代理模型替代迭代黑盒优化,实现单次前向传播获取近最优设计参数,在DDR5 DFE、SerDes均衡等场景中加速三到四个数量级。
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- 16 pages, 20 figures, 8 tables
高速信号完整性(SI)分析的布局前设计空间探索(DSE)通常受限于现代电子设计自动化(EDA)工作流程中仿真和迭代优化算法的计算成本。虽然机器学习代理模型加速了仿真步骤,但优化设计仍需利用迭代黑盒搜索方法。这种迭代性质扩展性差,使得多角点扫描计算成本高昂。作为解决方案,本文提出了用于布局前SI设计的摊销神经优化(ANO)。ANO通过利用完全可微的神经网络代理模型,完全消除了迭代黑盒推理。ANO从代理中提取解析梯度,以训练全局优化策略。推理时不再重复求解优化问题,而是离线学习优化过程,从而实现摊销。一旦ANO策略训练完成,它就能在单个确定性前向传播中直接将不同的通道上下文映射到近最优设计参数。基于三个复杂的SI设计场景展示了ANO框架的效率和准确性,包括DDR5决策反馈均衡(DFE)、9维SerDes Tx/Rx联合均衡以及DDR3 DQS差分对布线(在内部对偏斜约束下优化眼图指标)。与实例特定的黑盒算法相比,在牺牲约10%最优性的代价下,实现了三到四个数量级的加速。对于大规模32万实例多角点SerDes扫描优化,ANO将原本需要数天计算时间的迭代搜索算法压缩为一次批量前向传播,毫秒级完成。这将计算昂贵的SI优化转变为实时、交互式的布局前DSE。
Pre-layout design space exploration (DSE) for high-speed signal integrity (SI) analysis is often limited by the computational cost of simulations and iterative optimization algorithms within modern electronic design automation (EDA) workflows. While machine learning surrogate models accelerate the simulation step, optimizing designs still requires utilizing iterative black-box search methods. This iterative nature scales poorly, making multi-corner sweeps computationally expensive. As a solution, this paper proposes amortized neural optimization (ANO) for pre-layout SI design. ANO entirely eliminates iterative black-box inference by utilizing fully differentiable neural network surrogate models. ANO extracts analytical gradients from the surrogate to train a global optimization policy. Instead of solving the optimization problem repeatedly at inference, the optimization process is learned offline and therefore amortized. Once the ANO policy is trained, it maps different channel contexts directly to near-optimal design parameters in a single deterministic forward pass. The efficiency and accuracy of the ANO framework are demonstrated based on three complex SI design scenarios, including DDR5 decision feedback equalization (DFE), 9-dimensional SerDes Tx/Rx co-equalization, and DDR3 DQS differential pair routing to optimize eye diagram metrics under intra-pair skew constraints. By trading roughly 10% in optimality compared to instance-specific black-box algorithms, it realizes speedups of three to four orders of magnitude. For a large-scale 320,000-instance multi-corner SerDes sweep optimization, ANO collapses what would have taken days of computation using iterative search algorithms into a single batched forward pass that completes in milliseconds. This transforms computationally expensive SI optimization into real-time and interactive pre-layout DSE.