X-TIME: Accelerating Large Tree Ensembles Inference for Tabular Data With Analog CAMs

Structured, or tabular, data are the most common format in data science. While deep learning models have proven formidable in learning from unstructured data such as images or speech, they are less accurate than simpler approaches when learning from tabular data. In contrast, modern tree-based machine learning (ML) models shine in extracting relevant information from structured data. An essential requirement in data science is to reduce model inference latency in cases where, for example, models are used in a closed loop with simulation to accelerate scientific discovery. However, the hardware acceleration community has mostly focused on deep neural networks and largely ignored other forms of ML. Previous work has described the use of an analog content addressable memory (CAM) component for efficiently mapping random forests (RFs). In this work, we develop an analog-digital architecture that implements a novel increased precision analog CAM and a programmable chip for inference of state-of-the-art tree-based ML models, such as eXtreme Gradient Boosting (XGBoost), Categorical Boosting (CatBoost), and others. Thanks to hardware-aware training, X-TIME reaches state-of-the-art accuracy and $119\times $ higher throughput at $9740\times $ lower latency with ${\gt }150\times $ improved energy efficiency compared with a state-of-the-art GPU for models with up to 4096 trees and depth of 8, with a 19-W peak power consumption.