Populating Memory in Continual Learning with Consistency Aware Sampling

Continual Learning (CL) methods aim to mitigate Catastrophic Forgetting (CF), where knowledge from previously learned tasks is often lost in favor of the new one. Among those algorithms, some have shown the relevance of keeping a rehearsal buffer with previously seen examples, referred to as memory. Yet, despite their popularity, limited research has been done to understand which elements are more beneficial to store in memory. It is common for this memory to be populated through random sampling, with little guiding principles that may aid in retaining prior knowledge. In this paper, and consistent with previous work, we found that some storage policies behave similarly given a certain memory size or compute budget, but when these constraints are relevant, results differ considerably. Based on these insights, we propose CAWS (Consistency AWare Sampling), an original storage policy that leverages a learning consistency score (C-Score) to populate the memory with elements that are easy to learn and representative of previous tasks. Because of the impracticality of directly using the C-Score in CL, we propose more feasible and efficient proxies to calculate the score that yield state-of-the-art results on CIFAR-100 and Tiny Imagenet.