Piggyback: Adding Multiple Tasks to a Single, Fixed Network by Learning to Mask
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This work presents a method for adding multiple tasks to a single, fixed deep neural network without affecting performance on already learned tasks. By building upon concepts from network quantization and sparsification, we learn binary masks that "piggyback", or are applied to an existing network to provide good performance on a new task. These masks are learned in an end-to-end differentiable fashion, and incur a low overhead of 1 bit per network parameter, per task. Even though the underlying network is fixed, the ability to mask certain weights allows for the learning of a large number of filters. We show improved performance on a variety of classification tasks, including those with large domain shifts from the natural images of ImageNet. Unlike prior work, we can augment the capabilities of a network without suffering from catastrophic forgetting or competition between tasks, while incurring the least overhead per added task. We demonstrate the applicability of our method to multiple architectures, and obtain accuracies comparable with individual networks trained per task.
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