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$\texttt{MoE-RBench}$: Towards Building Reliable Language Models with Sparse Mixture-of-Experts
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Introduces MoE-RBench, a reliability benchmark assessing sparse MoE LLMs versus dense counterparts on safety/hallucination, adversarial robustness, and OOD robustness, and studies training and inference recipes to improve MoE reliability.
Problem
Reliability of sparse Mixture-of-Experts language models is under-evaluated compared with dense LLMs, and MoE models sometimes underperform dense models when fine-tuned on new domains.
Approach
A multi-dimensional reliability benchmark for SMoE that compares MoE models against matched dense models on harmfulness, hallucination, adversarial NLI, and style-based OOD robustness, plus an empirical study of MoE-specific training settings (aux loss, expert dropout, router training) and contrastive decoding (DoLa).
Key results
- Switch-base outperforms t5-base by about 2.1% on adversarial RA and 2.2% on standard RA; MoLM-350M-K2 beats pythia-410M by 2.6% on adversarial RA.
- On TruthfulQA MC, dense models outperform all MoLM variants and LlamaMoE-3.5B-K2, while MoE models win on Natural Questions exact match (e.g., LlamaMoE-3.5B-K4 19.92 vs OpenLlama-3B 16.09).
- Non-zero load-balancing loss (1e-3) raises generalization for switch-base (50.41 vs 49.63) and MoLM-350M-K2 (47.31 vs 45.16); larger expert dropout (0.2-0.3) improves accuracy and generalization.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| replace the dense T5-base with Switch Transformer | T5-base · SNLI-hard (standard-trained) | accuracy: 80.20 -> 82.40 | Helped |
| replace Pythia-410M with MoLM-350M-K2 | Pythia-410M · Natural Questions | Exact Match: 1.77 -> 3.74 | Helped |
| replace Pythia-410M with MoLM-350M-K2 | Pythia-410M · TruthfulQA MC1 | MC1: 23.38 -> 21.54 | Hurt |
| replace OpenLlama-3B with LlamaMoE-3B-K2 | OpenLlama-3B · TruthfulQA MC1 | MC1: 23.13 -> 25.09 | Helped |
| replace T5-base with switch-base | T5-base · ANLI average (adversarial-trained) | accuracy: +2.1% | Helped |
| replace OpenLlama-3B with LlamaMoE-3B-K2 | OpenLlama-3B · ANLI average (adversarial-trained) | accuracy: +2.0% | Helped |
| replace T5-base with switch-base | T5-base · SST-2 Style-OOD | accuracy: +2.35% | Helped |
| replace Pythia-410M with MoLM-350M-K2 | Pythia-410M · SST-2 Style-OOD | accuracy: 89.3 -> 92.2 | Helped |
| set auxiliary load-balance loss weight to 1e-3 rather than 0 (ablation) | switch-base · NLI | generalization: 49.63 -> 50.41 | Helped |
| set auxiliary load-balance loss weight to 1e-3 rather than 0 (ablation) | MoLM-350M-K2 · NLI | generalization: 45.16 -> 47.31 | Helped |
| increase expert dropout rate from 1e-1 to 2e-1 with routers frozen (ablation) | switch-base · NLI | generalization: 49.43 -> 52.15 | Helped |
| train with routers free rather than frozen (ablation) | MoLM-350M-K2 · NLI | accuracy: 84.70 -> 84.82 | Helped |
Surprising findings
- Bi-level (alternating router/backbone) training gives minimal or negative gains for LLM MoE, unlike CNN MoE results.
- Larger MoLM variant underperforms smaller one on TruthfulQA, an inverse-scaling pattern extended to MoE.
Limitations
- Relies on small models (up to about 3.5B) and few MoE architectures, with mismatched dense counterparts in size and training data.
- Adversarial and OOD evaluations use NLI and sentiment tasks; safety evaluation relies on automated judges rather than human annotation.
Experimental setup
Datasets: Alpaca SNLI ANLI SST-2 BOSS MaliciousInstructions CoNa Controversial Do-not-answer TruthfulQA Natural Questions
Benchmarks: SNLI SNLI-hard ANLI SST-2 style OOD BOSS TruthfulQA Natural Questions MaliciousInstructions CoNa Controversial Do-not-answer
Metrics: accuracy harmfulness score unsafe ratio exact match MC1/MC2/MC3
Baselines: T5-base pythia-410M pythia-1.4B OpenLlama-3B
Builds on: Switch Transformers ModuleFormer LLaMA-MoE DoLa BOSS benchmark
Closest papers by meaning
- Pruning and Distilling Mixture-of-Experts into Dense Language Models (NeurIPS 2026 · similarity 0.90)
- Advancing Expert Specialization for Better MoE (NeurIPS 2025 · similarity 0.89)
- Parameters vs FLOPs: Scaling Laws for Optimal Sparsity for Mixture-of-Experts Language Models (ICML 2025 · similarity 0.89)
- Your Mixture-of-Experts LLM Is Secretly an Embedding Model for Free (ICLR 2025 · similarity 0.89)
- Mixture of Experts Made Intrinsically Interpretable (ICML 2025 · similarity 0.89)
- FlexMoE: One-for-All Nested Intra-Expert Pruning for MoE Language Models (NeurIPS 2026 · similarity 0.89)
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