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Multi-Task Dense Prediction via Mixture of Low-Rank Experts
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Proposes MLoRE, a decoder-side mixture-of-experts for multi-task dense prediction that adds a task-shared generic convolution path and linear low-rank experts that re-parameterize into a single conv at inference.
Problem
Mixture-of-experts decoders for multi-task dense prediction struggle to model global relations among all tasks and adding experts greatly increases parameters and FLOPs.
Approach
Add a task-sharing generic 3x3 convolution path in parallel with MoE so all tasks share explicit parameters, and make experts low-rank (3x3 then 1x1 conv, no activations) so many experts are cheap and can be re-parameterized into one conv per task at inference.
Key results
- On PASCAL-Context with ViT-large, MLoRE reaches 81.41 semseg mIoU, 70.52 parsing mIoU, and 75.42 boundary odsF, exceeding TaskExpert (80.64, 69.42, 73.30).
- On NYUD-v2, MLoRE achieves 55.96 semseg mIoU, 0.5076 depth RMSE, 18.33 normals mErr, and 78.43 boundary odsF, the best on all four tasks.
- Low-rank experts cut parameters by over 60% versus standard MoE (e.g., 15 experts: 6.3M vs 29.9M for 3x3 setting per Table 1 comparisons) and the efficient ViT-small variant uses about 35% of TaskExpert's GFLOPs (72G vs 204G).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add the task-sharing generic convolution path to the low-rank expert path (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -1.71 -> -0.88 | Helped |
| add a task-specific low-rank expert path (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -0.88 -> -0.58 | Helped |
| replace standard MoE experts with low-rank expert networks (ablation) | ViT-base baseline on PASCAL-Context · PASCAL-Context | MTL ∆m: -1.20 -> -1.71 | Hurt |
| use varied task-sharing expert ranks from 16 to 128 instead of uniform rank 16 (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -0.77 -> -0.58 | Helped |
| use varied task-sharing expert ranks from 16 to 128 instead of uniform rank 128 (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -1.07 -> -0.58 | Helped |
| add a position-aware branch to the basic router (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -0.75 -> -0.58 | Helped |
| replace the basic router with a position-only router (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -0.75 -> -0.82 | Hurt |
| replace sample-dependent router input with learnable parameters (ablation) | MLoRE on PASCAL-Context · PASCAL-Context | MTL ∆m: -0.75 -> -0.91 | Hurt |
| activate 60% of experts rather than all expert networks (ablation) | MLoRE · PASCAL-Context | MTL gain | Helped |
| increase the number of task-sharing experts to 15 (ablation) | MLoRE · PASCAL-Context | MTL gain | Helped |
| use the full MLoRE method instead of TaskExpert | ViT-large multi-task model · PASCAL-Context | mIoU: 80.89 -> 81.41 | Helped |
| use the full MLoRE method instead of TaskExpert | ViT-large multi-task model · PASCAL-Context | odsF: 73.30 -> 75.42 | Helped |
Surprising findings
- Without the generic path, almost no expert is activated by all tasks in one sample, supporting the claim that standard decoder MoE fails to capture global task relations.
- Activating all experts hurts performance noticeably, so sparsity (about 60% of experts per task) matters for feature discrimination.
Limitations
- Evaluated only on two indoor/scene multi-task datasets (PASCAL-Context and NYUD-v2).
- Stop-gradient on the task-sharing generic path is a heuristic choice motivated by empirical gradient conflict observations.
- Compute hardware is not stated in the text.
Experimental setup
Datasets: PASCAL-Context NYUD-v2
Benchmarks: PASCAL-Context NYUD-v2
Metrics: mIoU maxF mErr odsF RMSE MTL gain delta-m FLOPs parameters
Baselines: PAD-Net MTI-Net ATRC InvPT TaskPrompter TaskExpert M3ViT Mod-Squad
Builds on: Mixture of Experts LoRA TaskPrompter InvPT M3ViT
Closest papers by meaning
- Multilinear Mixture of Experts: Scalable Expert Specialization through Factorization (NeurIPS 2024 · similarity 0.89)
- On the Expressive Power of Mixture-of-Experts for Structured Complex Tasks (NeurIPS 2025 · similarity 0.87)
- Multi-Head Mixture-of-Experts (NeurIPS 2024 · similarity 0.87)
- Pruning and Distilling Mixture-of-Experts into Dense Language Models (NeurIPS 2026 · similarity 0.87)
- Exploiting Activation Sparsity with Dense to Dynamic-k Mixture-of-Experts Conversion (NeurIPS 2024 · similarity 0.87)
- Joint MoE Scaling Laws: Mixture of Experts Can Be Memory Efficient (ICML 2025 · similarity 0.86)
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