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Independent Component Alignment for Multi-Task Learning (2305.19000v1)

Published 30 May 2023 in cs.CV and cs.LG

Abstract: In a multi-task learning (MTL) setting, a single model is trained to tackle a diverse set of tasks jointly. Despite rapid progress in the field, MTL remains challenging due to optimization issues such as conflicting and dominating gradients. In this work, we propose using a condition number of a linear system of gradients as a stability criterion of an MTL optimization. We theoretically demonstrate that a condition number reflects the aforementioned optimization issues. Accordingly, we present Aligned-MTL, a novel MTL optimization approach based on the proposed criterion, that eliminates instability in the training process by aligning the orthogonal components of the linear system of gradients. While many recent MTL approaches guarantee convergence to a minimum, task trade-offs cannot be specified in advance. In contrast, Aligned-MTL provably converges to an optimal point with pre-defined task-specific weights, which provides more control over the optimization result. Through experiments, we show that the proposed approach consistently improves performance on a diverse set of MTL benchmarks, including semantic and instance segmentation, depth estimation, surface normal estimation, and reinforcement learning. The source code is publicly available at https://github.com/SamsungLabs/MTL .

Citations (31)

Summary

  • The paper proposes Aligned-MTL, a novel optimization strategy for multi-task learning that improves training stability by minimizing the condition number of the gradient system.
  • Empirical evaluations on diverse benchmarks, including NYUv2 and CityScapes, demonstrate that Aligned-MTL consistently outperforms existing methods in performance and convergence stability.
  • Aligned-MTL offers significant implications for deploying multi-task models in resource-constrained environments and highlights the importance of numerical stability in deep learning optimization.

Independent Component Alignment for Multi-Task Learning: An Overview

The paper "Independent Component Alignment for Multi-Task Learning" addresses the optimization challenges inherent in multi-task learning (MTL) due to conflicting and dominating gradients. MTL involves training a single model to simultaneously handle multiple tasks, which can enhance overall performance and resource efficiency. However, the interaction between gradients of different tasks often leads to training instability and a compromised optimization process.

Theoretical Framework and Proposed Solution

The core contribution of this work is the introduction of a novel stability criterion for MTL—using the condition number of a linear system of gradients. The authors propose that the condition number effectively indicates stability in the training process by reflecting issues of gradient conflict and dominance. The condition number, defined as the ratio of the maximum to the minimum singular value of the gradient matrix, serves as a measure of stability. A well-conditioned system, indicated by a condition number close to one, implies minimal conflict and dominance among task gradients.

Building on this insight, the paper presents Aligned-MTL, an optimization strategy that aligns the orthogonal components of the linear system of gradients. This alignment minimizes the condition number, promoting stability in the gradient optimization process. Unlike previous MTL approaches that focus solely on convergence to a minimum, Aligned-MTL guarantees convergence to an optimal point while maintaining pre-defined task-specific weights. This offers notable advantages in terms of task performance balance and stability.

Empirical Evaluation and Results

The efficacy of Aligned-MTL is demonstrated through rigorous experiments on various MTL benchmarks. The experiments cover diverse tasks such as semantic segmentation, instance segmentation, depth estimation, surface normal estimation, and reinforcement learning scenarios. The results consistently show superior performance over existing methods, with Aligned-MTL demonstrating more stable and efficient convergence.

Aligned-MTL outperforms both conventional heuristic-based weighting techniques and recent gradient manipulation methods that attempt to resolve specific aspects of MTL challenges. The paper highlights its effectiveness using synthetic benchmarks and real-world datasets like NYUv2 and CityScapes, providing a significant improvement in overall task performance compared to both baseline and advanced MTL methods.

Implications and Future Directions

The implications of Aligned-MTL are significant for the development of multi-tasking models in resource-constrained environments, like mobile and edge devices, where computational resources must be judiciously allocated. The approach aligns with a growing trend towards models that can perform well across multiple domains without requiring separate models for each task, thus saving both memory and computational power.

In terms of theoretical advancement, the work presents a compelling case for broader exploration and application of numerical stability concepts in the optimization of deep learning models. By extending these theoretical insights and practical implementations, future work could explore further optimizations for specific architectures or tasks and potentially develop adaptive solutions that incrementally adjust the optimization criteria based on dynamic task interactions.

Conclusion

In conclusion, "Independent Component Alignment for Multi-Task Learning" provides a robust theoretical and empirical evaluation of training stability for MTL settings. By aligning gradient components to minimize the condition number, the proposed Aligned-MTL offers a promising direction for achieving stable and equitable task performance across multiple objectives. As the field of AI continues its march towards multi-functional models, approaches like Aligned-MTL will be instrumental in balancing efficiency, performance, and stability.

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