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Awesome-Forgetting-in-Deep-Learning

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A comprehensive list of papers about 'A Comprehensive Survey of Forgetting in Deep Learning Beyond Continual Learning'.

Abstract

Forgetting refers to the loss or deterioration of previously acquired information or knowledge. While the existing surveys on forgetting have primarily focused on continual learning, forgetting is a prevalent phenomenon observed in various other research domains within deep learning. Forgetting manifests in research fields such as generative models due to generator shifts, and federated learning due to heterogeneous data distributions across clients. Addressing forgetting encompasses several challenges, including balancing the retention of old task knowledge with fast learning of new tasks, managing task interference with conflicting goals, and preventing privacy leakage, etc. Moreover, most existing surveys on continual learning implicitly assume that forgetting is always harmful. In contrast, our survey argues that forgetting is a double-edged sword and can be beneficial and desirable in certain cases, such as privacy-preserving scenarios. By exploring forgetting in a broader context, we aim to present a more nuanced understanding of this phenomenon and highlight its potential advantages. Through this comprehensive survey, we aspire to uncover potential solutions by drawing upon ideas and approaches from various fields that have dealt with forgetting. By examining forgetting beyond its conventional boundaries, in future work, we hope to encourage the development of novel strategies for mitigating, harnessing, or even embracing forgetting in real applications.

Citation

If you find our paper or this resource helpful, please consider cite:

@article{Forgetting_Survey_2023,
  title={A Comprehensive Survey of Forgetting in Deep Learning Beyond Continual Learning},
  author={Wang, Zhenyi and Yang, Enneng and Shen, Li and Huang, Heng},
  journal={arXiv preprint arXiv:2307.09218},
  year={2023}
}

Thanks!

Framework

• Harmful Forgetting
  • Forgetting in Continual Learning
    • Survey and Book
    • Task-aware CL
      • Memory-based Methods
      • Architecture-based Methods
      • Regularization-based Methods
      • Subspace-based Methods
      • Bayesian Methods
    • Task-free CL
    • Online CL
    • Semi-supervised CL
    • Few-shot CL
    • Unsupervised CL
    • Theoretical Analysis
  • Forgetting in Foundation Models
    • Forgetting in Fine-Tuning Foundation Models
    • Forgetting in One-Epoch Pre-training
    • CL in Foundation Model
  • Forgetting in Domain Adaptation
  • Forgetting in Test-Time Adaptation
  • Forgetting in Meta-Learning
    • Incremental Few-Shot Learning
    • Continual Meta-Learning
  • Forgetting in Generative Models
    • GAN Training is a Continual Learning Problem
    • Lifelong Learning of Generative Models
  • Forgetting in Reinforcement Learning
  • Forgetting in Federated Learning
    • Forgetting Due to Non-IID Data in FL
    • Federated Continual Learning
• Beneficial Forgetting
  • Forgetting Irrelevant Information to Achieve Better Performance
    • Combat Overfitting Through Forgetting
    • Learning New Knowledge Through Forgetting Previous Knowledge
  • Machine Unlearning

Harmful Forgetting

Harmful forgetting occurs when we desire the machine learning model to retain previously learned knowledge while adapting to new tasks, domains, or environments. In such cases, it is important to prevent and mitigate knowledge forgetting.

Links: <u> Forgetting in Continual Learning </u> | <u> Forgetting in Foundation Models </u> | <u> Forgetting in Domain Adaptation</u> | <u> Forgetting in Test-Time Adaptation</u> |
<u> Forgetting in Meta-Learning </u>|
<u> Forgetting in Generative Models </u>| <u> Forgetting in Reinforcement Learning</u> | <u> Forgetting in Federated Learning</u>

Forgetting in Continual Learning

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The goal of continual learning (CL) is to learn on a sequence of tasks without forgetting the knowledge on previous tasks.

Links: <u> Task-aware CL </u>| <u> Task-free CL </u>| <u> Online CL </u>| <u> Semi-supervised CL </u>| <u> Few-shot CL </u>| <u> Unsupervised CL </u>| <u> Theoretical Analysis </u>

Survey and Book

Task-aware CL

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Task-aware CL focuses on addressing scenarios where explicit task definitions, such as task IDs or labels, are available during the CL process. Existing methods on task-aware CL have explored five main branches: Memory-based Methods | Architecture-based Methods | Regularization-based Methods | Subspace-based Methods | Bayesian Methods.

Memory-based Methods

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Memory-based (or Rehearsal-based) method keeps a memory buffer that stores the examples/knowledges from previous tasks and replay those examples during learning new tasks.

Architecture-based Methods

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The architecture-based approach avoids forgetting by reducing parameter sharing between tasks or adding parameters to new tasks.

Regularization-based Methods

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Regularization-based approaches avoid forgetting by penalizing updates of important parameters or distilling knowledge with previous model as a teacher.

Subspace-based Methods

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Subspace-based methods perform CL in multiple disjoint subspaces to avoid interference between multiple tasks.

Bayesian Methods

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Bayesian methods provide a principled probabilistic framework for addressing Forgetting.

Task-free CL

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Task-free CL refers to a specific scenario that the learning system does not have access to any explicit task information.

Online CL

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In online CL, the learner is only allowed to process the data for each task once.

The presence of imbalanced data streams in CL (especially online CL) has drawn significant attention, primarily due to its prevalence in real-world application scenarios.

Semi-supervised CL

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Semi-supervised CL is an extension of traditional CL that allows each task to incorporate unlabeled data as well.

Few-shot CL

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Few-shot CL refers to the scenario where a model needs to learn new tasks with only a limited number of labeled examples per task while retaining knowledge from previously encountered tasks.

Unsupervised CL

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Unsupervised CL (UCL) assumes that only unlabeled data is provided to the CL learner.

Theoretical Analysis

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Theory or analysis of continual learning

Forgetting in Foundation Models

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Foundation models are large machine learning models trained on a vast quantity of data at scale, such that they can be adapted to a wide range of downstream tasks.

Links: Forgetting in Fine-Tuning Foundation Models | Forgetting in One-Epoch Pre-training | CL in Foundation Model

Forgetting in Fine-Tuning Foundation Models

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When fine-tuning a foundation model, there is a tendency to forget the pre-trained knowledge, resulting in sub-optimal performance on downstream tasks.

Forgetting in One-Epoch Pre-training

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Foundation models often undergo training on a dataset for a single pass. As a result, the earlier examples encountered during pre-training may be overwritten or forgotten by the model more quickly than the later examples.

CL in Foundation Model

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By leveraging the powerful feature extraction capabilities of foundation models, researchers have been able to explore new avenues for advancing continual learning techniques.

Forgetting in Domain Adaptation

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The goal of domain adaptation is to transfer the knowledge from a source domain to a target domain.

Forgetting in Test-Time Adaptation

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Test time adaptation (TTA) refers to the process of adapting a pre-trained model on-the-fly to unlabeled test data during inference or testin.

Forgetting in Meta-Learning

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Meta-learning, also known as learning to learn, focuses on developing algorithms and models that can learn from previous learning experiences to improve their ability to learn new tasks or adapt to new domains more efficiently and effectively.

Links: Incremental Few-Shot Learning | Continual Meta-Learning

Incremental Few-Shot Learning

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Incremental few-shot learning (IFSL) focuses on the challenge of learning new categories with limited labeled data while retaining knowledge about previously learned categories.

Continual Meta-Learning

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The goal of continual meta-learning (CML) is to address the challenge of forgetting in non-stationary task distributions.

Forgetting in Generative Models

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The goal of a generative model is to learn a generator that can generate samples from a target distribution.

Links: GAN Training is a Continual Learning Problem | Lifelong Learning of Generative Models

GAN Training is a Continual Learning Problem

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Treating GAN training as a continual learning problem.

Lifelong Learning of Generative Models

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The goal is to develop generative models that can continually generate high-quality samples for both new and previously encountered tasks.

Forgetting in Reinforcement Learning

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Reinforcement learning is a machine learning technique that allows an agent to learn how to behave in an environment by trial and error, through rewards and punishments.

Forgetting in Federated Learning

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Federated learning (FL) is a decentralized machine learning approach where the training process takes place on local devices or edge servers instead of a centralized server.

Links: Forgetting Due to Non-IID Data in FL | Federated Continual Learning

Forgetting Due to Non-IID Data in FL

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This branch pertains to the forgetting problem caused by the inherent non-IID (not identically and independently distributed) data among different clients participating in FL.

Federated Continual Learning

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This branch addresses the issue of continual learning within each individual client in the federated learning process, which results in forgetting at the overall FL level.

Beneficial Forgetting

<a href="#top">[Back to top]</a> Beneficial forgetting arises when the model contains private information that could lead to privacy breaches or when irrelevant information hinders the learning of new tasks. In these situations, forgetting becomes desirable as it helps protect privacy and facilitate efficient learning by discarding unnecessary information.

Links: <u>Combat Overfitting Through Forgetting</u> | <u>Learning New Knowledge Through Forgetting Previous Knowledge</u> | <u>Machine Unlearning</u>

Forgetting Irrelevant Information to Achieve Better Performance

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Combat Overfitting Through Forgetting

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Overfitting in neural networks occurs when the model excessively memorizes the training data, leading to poor generalization. To address overfitting, it is necessary to selectively forget irrelevant or noisy information.

Learning New Knowledge Through Forgetting Previous Knowledge

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"Learning to forget" suggests that not all previously acquired prior knowledge is helpful for learning new tasks.

Machine Unlearning

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Machine unlearning, a recent area of research, addresses the need to forget previously learned training data in order to protect user data privacy.

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Contact

We welcome all researchers to contribute to this repository 'forgetting in deep learning'.

Email: wangzhenyineu@gmail.com | ennengyang@stumail.neu.edu.cn