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Sign-MAML: Efficient Model-Agnostic Meta-Learning by SignSGD
Chen Fan · Parikshit Ram · Sijia Liu

@
in 5th Workshop on Meta-Learning »
Event URL: https://openreview.net/forum?id=bd0UOwKS_6j »

We propose a new computationally-efficient first-order algorithm for Model-Agnostic Meta-Learning (MAML). The key enabling technique is to interpret MAML as a bilevel optimization (BLO) problem and leverage the sign-based SGD (signSGD) as a lower-level optimizer of BLO. We show that MAML, through the lens of signSGD-oriented BLO, naturally yields an alternating optimization scheme that just requires first-order gradients of a learned meta-model. We term the resulting MAML algorithm Sign-MAML. Compared to the conventional first-order MAML (FO-MAML) algorithm, Sign-MAML is theoretically-grounded as it does not impose any assumption on the absence of second-order derivatives during meta training. In practice, we show that Sign-MAML outperforms FO-MAML in various few-shot image classification tasks, and compared to MAML, it achieves a much more graceful tradeoff between classification accuracy and computation efficiency.

Author Information

Chen Fan (University of Massachusetts, Amherst)
Parikshit Ram (IBM Research AI)
Sijia Liu (Michigan State University)

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