Beyond solving static datasets: Deep learning from streaming data

Project Information

KeepOnLearning

Grant agreement ID: 101021347

DOI

10.3030/101021347

EC signature date 21 August 2021

Start date 1 September 2021

End date 31 August 2027

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 499 065,00

EU contribution

€ 2 499 065,00

Coordinated by

KATHOLIEKE UNIVERSITEIT LEUVEN
Belgium

Periodic Reporting for period 3 - KeepOnLearning (Beyond solving static datasets: Deep learning from streaming data)

Reporting period: 2024-09-01 to 2026-02-28

Summary of the context and overall objectives of the project

Data is key for modern AI solutions, especially those based on deep neural networks. Unfortunately, the data-driven nature of deep learning that makes it so powerful when dealing with complex and high-dimensional data, is also at the core of its main weakness: a model is only as good as the data it builds on. Standard machine learning practice relies on the training data being representative for data encountered during system deployment. This is perfect when working with stationary datasets. Yet in practice, data distributions are often non-stationary, i.e. they change over time. This can have a multitude of reasons – think of social trends, seasonal or geographic variations, or changing user requirements. One would think that it suffices to finetune the models with the new data. However, this leads to a phenomenon known as 'catastrophic forgetting': the model overfits to the new data and completely forgets what it has learned previously. As data distributions change, it is therefore common practice to regularly retrain the models all over again. This is expensive, time consuming and ecologically unfriendly.

With the KeepOnLearning project, we aim to build a new generation of deep learning methods, able to adapt to new conditions by continuously updating the models based on new training data becoming available. Learning from non-stationary streaming data is, however, still a major challenge requiring fundamental research. To reach our goal, we build on our earlier expertise in continual learning, and plan to tightly link continual learning with advances in self-supervised representation learning and multimodal learning. If successful, this will lead to machine learning systems that keep on learning over time, systematically improving their skills and never getting outdated. It also may lower the threshold for applying machine learning, as it reduces the need for a skilled data scientist carefully preparing the data beforehand. As a practical application, we plan to showcase our work’s feasibility, scalability and flexibility in the context of automatic generation of audio descriptions of videos for the visually impaired.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

To tackle the problem of continual learning from non-stationary data streams, during the first half of the project we mainly focused our research efforts along the following axes:

1. Better understanding of the learning dynamics leading to catastrophic forgetting
We consolidated a principled taxonomy of continual learning setups; we studied where in a neural network the forgetting is most severe; and we discovered that forgetting is most outspoken immediately after switching to a new task. The latter is important, as it means the worst case performance of a continual learning system is much lower than what one would expect based on previous more coarse evaluation metrics. This has a severe impact on the use of continual learning in safety-critical applications.

2. Methods to prevent catastrophic forgetting
We proposed a first method to tackle the catastrophic forgetting, that does not require storing old samples in a memory buffer and is especially well suited for the realistic case of just a single pass through the data.

3. Better self-supervised representation learning models
Based on our findings on the learning dynamics, it became evident that good representations are key in tackling the catastrophic forgetting issue: networks that have learned to extract powerful representations can learn new tasks more easily, with less interference and hence less forgetting. This motivated us to look closer into representation learning. The fact that these are typically trained in a self-supervised setting, i.e. without requiring human annotations, is an extra advantage, as it makes them well suited for a continual learning setup, where labels are often hard to get.
In particular, we developed a method that discovers semantic concepts in images and learns local representations based on them, leading to state-of-the-art results on a variety of dense downstream tasks under a low data regime, even without any retraining ('in context inference').

3. Better multimodal learning models
We identified the co-occurrence among different modalities (e.g. vision and language) as an important cue to learn in a self-supervised or weakly supervised manner. So far, we focused on human-object interaction detection, where we proposed a zero-shot solution.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We now have a better understanding of the process of catastrophic forgetting. We have learned that good representations are key for continual learning, and have also made progress in that direction.
The next major step is to scale up. Instead of focusing on small sequences of tasks that are learned from scratch, starting from the best possible pretrained representation learner makes sense.
These are often large models, which require special parameter efficient methods for adaptation. The use case of automatic generation of audio descriptions will drive our research in that direction, integrating the advances in representation learning, multimodal learning and continual learning.

Illustration of continual learning