# Continual learning

tags
Machine learning

Continual learning is a type of supervised learning where there is no “testing phase” associated to a decision process. Instead, training samples keep being processed by the algorithm which has to simultaneously make predictions and keep learning.

This is challenging for a fixed neural network architecture since it has a fixed capacity and is bound to either forget things or be unable to learn anything new.

A definition from the survey (De Lange et al. 2020):

The General Continual Learning setting considers an infinite stream of training data where at each time step, the system receives a (number of) new sample(s) drawn non i.i.d from a current distribution that could itself experience sudden of gradual changes.

## Benchmarks

### Computer vision based benchmarks

• Split MNIST: the MNIST dataset is split into 5 2-classes tasks.

• Split CIFAR10: the CIFAR10 dataset is split into 5 2-classes tasks.

• Split mini-ImageNet: a mini ImageNet (100 classes) task split into 20 5-classes tasks.

• Continual Transfer Learning Benchmark: A benchmark from Facebook AI, built from 7 computer vision datasets: MNIST, CIFAR10, CIFAR100, DTD, SVHN, Rainbow-MNIST, Fashion MNIST. The tasks are all 5-classes or 10-classes classification tasks. Some example task sequence constructions from (Veniat, Denoyer, and Ranzato 2021):

The last task of $$S_out$$ consists of a shuffling of the output labels of the first task. The last task of $$S_in$$ is the same as its first task except that MNIST images have a different background color. $$S_long$$ has 100 tasks, and it is constructed by first sampling a dataset, then 5 classes at random, and finally the amount of training data from a distribution that favors small tasks by the end of the learning experience.

• Permuted MNIST: here for each different task the pixels of the MNIST digits are permuted, generating a new task of equal difficulty as the original one but different solution. This task is not suitable if the model has some spatial prior (like a CNN). Used first in (Kirkpatrick et al. 2017).

• Rotated MNIST: each task contains digits rotated by a fixed angle between 0 and 180 degrees.

## Bibliography

1. . . "Toward an Architecture for Never-Ending Language Learning.". In Proceedings of the Conference on Artificial Intelligence (AAAI) (2010), 1306–13. DOI.

2. . . “A Continual Learning Survey: Defying Forgetting in Classification Tasks”. arXiv:1909.08383 [Cs, Stat]. http://arxiv.org/abs/1909.08383.

3. . . “Overcoming Catastrophic Forgetting in Neural Networks”. arXiv:1612.00796 [Cs, Stat]. http://arxiv.org/abs/1612.00796.

4. . . “Efficient Continual Learning with Modular Networks and Task-Driven Priors”. arXiv:2012.12631 [Cs]. http://arxiv.org/abs/2012.12631.