A Review of Meta-Reinforcement Learning for Deep Neural Networks Architecture Search

The plain network design is generally kept as a first step of proposed approaches application ([28], [42]) given that it leads to simple networks and allows to focus on the method itself before switching to more complex structures with modular design ([29], [49]). A third option used in design approaches at a lower scale is the prediction of explored architectures rewards before full training the most promising ones ([25], [29]). This training acceleration technique is implemented for performance improvement purpose and requires further attention to control possible bias impact on the models behavior. The success of current reinforcement-learning-based approaches to design CNN architectures is widely proven especially for image classification tasks. However, it is achieved at the cost of high computational resources despite the acceleration attempts of most of recent models. Such fact is preventing individual researchersand small research entities (companies and laboratories) from fully access to this innovative technology [42]. Hence, deeper and more revolutionary optimizing methods are required to practically operate CNN automatic design. Transformation approaches based on extended network morphisms [49] are among the first attempts in this direction that achieved drastic decrease in computational cost and demonstrated generalization capacity. Additionalfuture directions to control automatic design complexity is to develop methods for multi-task problems [58] and weights sharing [59] in order to benefit from knowledge transfer contributions.