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Hymba: A Hybrid-head Architecture for Small Language Models

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arxiv 2411.13676 v1 pith:BXRPKTYD submitted 2024-11-20 cs.CL cs.AIcs.LG

Hymba: A Hybrid-head Architecture for Small Language Models

classification cs.CL cs.AIcs.LG
keywords attentionmodelsarchitecturehymbasmallcacheheadshybrid-head
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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We propose Hymba, a family of small language models featuring a hybrid-head parallel architecture that integrates transformer attention mechanisms with state space models (SSMs) for enhanced efficiency. Attention heads provide high-resolution recall, while SSM heads enable efficient context summarization. Additionally, we introduce learnable meta tokens that are prepended to prompts, storing critical information and alleviating the "forced-to-attend" burden associated with attention mechanisms. This model is further optimized by incorporating cross-layer key-value (KV) sharing and partial sliding window attention, resulting in a compact cache size. During development, we conducted a controlled study comparing various architectures under identical settings and observed significant advantages of our proposed architecture. Notably, Hymba achieves state-of-the-art results for small LMs: Our Hymba-1.5B-Base model surpasses all sub-2B public models in performance and even outperforms Llama-3.2-3B with 1.32% higher average accuracy, an 11.67x cache size reduction, and 3.49x throughput.

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Forward citations

Cited by 26 Pith papers

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