  In continual learning, the learner faces a stream of data whose distribution
changes over time. Modern neural networks are known to suffer under this
setting, as they quickly forget previously acquired knowledge. To address such
catastrophic forgetting, many continual learning methods implement different
types of experience replay, re-learning on past data stored in a small buffer
known as episodic memory. In this work, we complement experience replay with a
new objective that we call anchoring, where the learner uses bilevel
optimization to update its knowledge on the current task, while keeping intact
the predictions on some anchor points of past tasks. These anchor points are
learned using gradient-based optimization to maximize forgetting, which is
approximated by fine-tuning the currently trained model on the episodic memory
of past tasks. Experiments on several supervised learning benchmarks for
continual learning demonstrate that our approach improves the standard
experience replay in terms of both accuracy and forgetting metrics and for
various sizes of episodic memories.
