Research map / Learning theory and algorithms / Fairness
Fair Resource Allocation in Multi-Task Learning
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Casts multi-task learning gradient conflict as α-fair utility maximization over task loss-decrease rates, yielding the FairGrad update, plus an α-fair loss transformation that boosts existing MTL methods.
Problem
Gradient conflicts in multi-task learning cause the update to be dominated by large gradients, hurting fair optimization of some tasks and overall MTL performance.
Approach
Model the common MTL update direction as an α-fair utility maximization (loss-decrease rates as utilities borrowed from network resource allocation), solve for task weights via a nonlinear least-squares problem, and separately apply an α-fair transformation to task losses to improve existing MTL methods.
Key results
- On Cityscapes (2-task), FairGrad achieves MR 1.50 and Δm% 5.18, versus Nash-MTL MR 3.25 and Δm% 6.82.
- On NYU-v2 (3-task), FairGrad achieves Δm% -4.66 and MR 2.67, the best among compared methods.
- On MT10 RL benchmark, FairGrad reaches 0.84 success rate, below Nash-MTL's reported 0.91 (original paper) but above several baselines.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use FairGrad instead of the best reported baseline | MTL methods · CelebA (40-task) | Δm% | Helped |
| use FairGrad instead of FAMO | MTL methods · QM9 (11-task) | Δm%: 58.5 -> 57.9 | Helped |
| use FairGrad instead of Nash-MTL | MTL methods · NYU-v2 (3-task) | MR: 3.11 -> 2.67 | Helped |
| use FairGrad instead of Nash-MTL | MTL methods · Cityscapes (2-task) | MR: 3.25 -> 1.50 | Helped |
| use FairGrad instead of Nash-MTL (reproduced) | SAC on MT10 · MT10 | success rate: 0.80 ± 0.13 -> 0.84 ± 0.07 | Helped |
| set α=2 rather than α=1 (ablation) | FairGrad · NYU-v2 (3-task) | Δm%: -2.79 -> -4.96 | Helped |
| vary α among 1, 2, 5, and 10 (ablation) | FairGrad · Cityscapes (2-task) | Δm%: 6.73; 3.90; 6.87; 10.54 | Mixed |
| add α-fair loss transformation (α=0.5) (ablation) | LS, RLW, DWA, UW, MGDA, PCGrad, and CAGrad · NYU-v2 (3-task) | Δm%: 5.59 -> 2.85; 7.78 -> 5.00; 3.57 -> 2.65; 4.05 -> 3.56; 1.38 -> -3.26; 3.97 -> 1.23; 0.20 -> -2.91 | Helped |
| add α-fair loss transformation (α=0.5) (ablation) | LS, RLW, DWA, MGDA, PCGrad, and CAGrad · Cityscapes (2-task) | Δm%: 22.60 -> 10.86; 24.38 -> 11.64; 21.45 -> 10.74; 44.14 -> 9.91; 18.29 -> 10.71; 11.64 -> 6.23 | Helped |
| add α-fair loss transformation (α=0.5) (ablation) | FairGrad · Cityscapes (2-task) | Δm%: 5.18 -> 4.92 | Helped |
| replace Nash-MTL's original subproblem solver with the authors' approach (ablation) | Nash-MTL · Cityscapes (2-task) | Δm%: 6.82 -> 6.28 | Helped |
Surprising findings
- Nash-MTL could not be reproduced exactly; reproduced result (0.80) was lower than reported (0.91).
- Applying the alpha-fair loss transformation to FairGrad gave only marginal improvement, unlike other methods which improved substantially.
Limitations
- Convergence theorem relies on linear independence of task gradients assumption outside Pareto stationary points.
- RL setting requires approximating the least-squares subproblem with SGD for time reasons.
- Best alpha requires tuning via search; MR and Δm% can disagree.
Experimental setup
Datasets: CelebA QM9 NYU-v2 Cityscapes MT10 (MetaWorld)
Benchmarks: CelebA QM9 NYU-v2 Cityscapes MT10
Metrics: Delta m% mean rank success rate
Baselines: Linear Scalarization Scale-Invariant RLW DWA UW MGDA PCGrad CAGrad IMTL-G Nash-MTL FAMO GradDrop
Builds on: Nash-MTL MGDA PCGrad CAGrad FAMO
Closest papers by meaning
- Revisiting Fairness in Multitask Learning: A Performance-Driven Approach for Variance Reduction (CVPR 2025 · similarity 0.91)
- FairMT: Fairness for Heterogeneous Multi-Task Learning (NeurIPS 2026 · similarity 0.90)
- Towards Consistent Multi-Task Learning: Unlocking the Potential of Task-Specific Parameters (CVPR 2025 · similarity 0.88)
- Bayesian Uncertainty for Gradient Aggregation in Multi-Task Learning (ICML 2024 · similarity 0.87)
- Delve into the Applicability of Advanced Optimizers for Multi-Task Learning (NeurIPS 2026 · similarity 0.87)
- Selective Task Group Updates for Multi-Task Optimization (ICLR 2025 · similarity 0.87)
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