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Domain-Specific Pruning of Large Mixture-of-Experts Models with Few-shot Demonstrations
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Proposes EASY-EP, a one-forward-pass domain-specific expert pruning method for large MoE models (DeepSeek-R1, DeepSeek-V3-0324) that scores experts by gating-weighted output norms and token-level representation change, using few-shot demonstrations.
Problem
Large fine-grained MoE models such as DeepSeek-R1 (671B, 256 experts per layer) require huge memory; existing expert pruning and merging methods are either unreliable at identifying key experts, too expensive with many experts, or designed for models with few experts.
Approach
Observes "few-shot expert localization": a handful of in-domain demonstrations reliably identifies a stable sparse expert subset. Scores each expert by the product of gating value and L2 norm of its output, weighted per token by 1 minus the cosine similarity between hidden states before and after routed experts, then keeps top-M experts in a single forward pass.
Key results
- On DeepSeek-R1 with 128 of 256 experts retained (domain-specific), EASY-EP averages 66.55 vs 67.20 for the full model, outperforming gating-score pruning (56.49).
- Under mixed-domain pruning with 128 experts, EASY-EP averages 61.47 on DeepSeek-R1 and 54.92 on DeepSeek-V3-0324 (full 54.08).
- Pruning to 128 experts yields 2.99x throughput and 64 experts yields 4.33x throughput versus the full DeepSeek-R1 model under SGLang (1K input/1K output).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add expert-level token contribution estimation (ablation) | EASY-EP with 64 experts · AIME-2024 | pass@1: 65.33 -> 72.81 | Helped |
| add expert-level token contribution estimation (ablation) | EASY-EP with 64 experts · LiveCodeBench | pass@1: 27.54 -> 42.51 | Helped |
| add expert-level token contribution estimation (ablation) | EASY-EP with 64 experts · GPQA-Diamond | pass@1: 56.57 -> 67.47 | Helped |
| add expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · AIME-2024 | pass@1: 70.00 -> 72.81 | Helped |
| add expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · LiveCodeBench | pass@1: 19.76 -> 42.51 | Helped |
| add expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · GPQA-Diamond | pass@1: 61.11 -> 67.47 | Helped |
| add both token contribution estimation and expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · AIME-2024 | pass@1: 2.67 -> 72.81 | Helped |
| add both token contribution estimation and expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · LiveCodeBench | pass@1: 0.00 -> 42.51 | Helped |
| add both token contribution estimation and expert output L2 norm weighting (ablation) | EASY-EP with 64 experts · GPQA-Diamond | pass@1: 20.20 -> 67.47 | Helped |
| use input plus model-generated output as calibration data instead of input-only data (ablation) | DeepSeek-R1 pruning · AIME-2024 | pass@1: 66.00 -> 79.17 | Helped |
| use CommonCrawl calibration data instead of input plus model-generated output (ablation) | DeepSeek-R1 pruning · AIME-2024 | pass@1: 79.17 -> 0.00 | Hurt |
| use layer-wise dynamic compression ratios instead of a fixed pruning ratio (ablation) | EASY-EP, DeepSeek-R1 at ratio 0.5 · LiveCodeBench | pass@1: 61.11 -> 44.31 | Hurt |
Surprising findings
- Pruning half the experts with EASY-EP matches or exceeds full-model performance on some domain benchmarks, which the authors attribute to removing irrelevant experts.
- Non-reasoning DeepSeek-V3-0324 is more robust to pruning than reasoning DeepSeek-R1, and its AgentBench-OS score even improves after pruning some experts.
Limitations
- Robustness differs between reasoning and non-reasoning models, validated on only two DeepSeek models.
- Pruning without any training/recovery; the authors leave in-domain vs out-of-domain balancing training to future work.
- Out-of-domain performance is typically poorer than mixed-domain pruning.
Experimental setup
Datasets: AIME-2023 GPQA-main LiveCodeBench-V3 AgentBench-OS dev set FinanceIQ dev set USMLE dev set
Benchmarks: AIME-2024 AIME-2025 HMMT-Feb 2025 LiveCodeBench GPQA-Diamond USMLE FinanceIQ AgentBench-OS
Metrics: pass@1 average accuracy throughput
Baselines: Random pruning Frequency pruning Gating score pruning M-SMoE
Builds on: Mixtral M-SMoE NAEE CD-MoE
Closest papers by meaning
- A Provably Effective Method for Pruning Experts in Fine-tuned Sparse Mixture-of-Experts (ICML 2024 · similarity 0.92)
- Pruning and Distilling Mixture-of-Experts into Dense Language Models (NeurIPS 2026 · similarity 0.91)
- Advancing Expert Specialization for Better MoE (NeurIPS 2025 · similarity 0.90)
- DiEP: Adaptive Mixture-of-Experts Compression through Differentiable Expert Pruning (NeurIPS 2025 · similarity 0.90)
- Solving Token Gradient Conflict in Mixture-of-Experts for Large Vision-Language Model (ICLR 2025 · similarity 0.90)
- FlexMoE: One-for-All Nested Intra-Expert Pruning for MoE Language Models (NeurIPS 2026 · similarity 0.89)
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