ARCHead: Activation-Metric Residual Correction for Large Language Model Output Heads
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Abstract (arXiv)
Weight-only quantization substantially reduces the storage of large language model (LLM) transformer blocks, but practical backends often retain the final language-modeling head (LM-head) in BF16 or FP16. Quantizing this projection naively can strongly perturb the vocabulary-logit distribution. We present ARCHead, a packed LM-head compressor that combines a quantized low-rank core, group-wise INT4 residuals, and a low-rank correction fitted in an activation-derived metric. ARCHead stores no dense BF16 head and reduces persistent LM-head storage by 3.7-3.9x. On Qwen3-8B-Base, it uses 25.6% of BF16 head storage while attaining 1.007 relative perplexity; storage-matched naive INT4 yields 1.14-1.16. Replacing the BF16 head left by AWQ or bitsandbytes adds only 0.006-0.007 cross-entropy, with less than 2% throughput change in our measurements. ARCHead therefore complements block quantizers by compressing the large output projection they can leave untouched. Code is available at https://github.com/suayptalha/archead.
Key facts. Cited by 1 paper in the map (data through 7 Oct 2026). Builds on 14 of its 23 references that are in the map. First posted on arXiv 3 Aug 2026.
Builds on
14 of 23 references.
References · 14
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- 2023SpQR: A Sparse-Quantized Representation for Near-Lossless LLM Weight Compressioncited by 359
- 2024QuIP#: Even Better LLM Quantization with Hadamard Incoherence and Lattice Codebookscited by 354
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Citing papers per year: 2026: 1.
1 paper.
- 2026Softmax Reparameterization for Output-Head Quantizationcited by 0
- 2026Softmax Reparameterization for Output-Head Quantization25 Sep 2026