amzn/pecos

Combines hierarchical label tree traversal with recursive linear models (X-Linear) and Transformer-based fine-tuning (XR-Transformer) to efficiently rank from 100MM+ label spaces in real-time. Integrates with Hugging Face Transformers for pre-trained model support and implements HNSW-based approximate nearest neighbor search with SIMD-optimized sparse/dense distance computation and multi-threaded inference.

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