Hyperparameter Optimization is the problem of choosing a set of optimal hyperparameters for a learning algorithm. Whether the algorithm is suitable for the data directly depends on hyperparameters, which directly influence overfitting or underfitting. Each model requires different assumptions, weights or training speeds for different types of data under the conditions of a given loss function.
Single-Headed Attention is a single-headed attention module used in the SHA-RNN language model. The principle design reasons for single-headedness were simplicity (avoiding running out of memory) and scepticism about the benefits of using multiple heads.
SHA-RNN, or Single Headed Attention RNN, is a recurrent neural network, and language model when combined with an embedding input and softmax classifier, based on a core LSTM component and a single-headed attention module. Other design choices include a Boom feedforward layer and the use of layer normalization. The guiding principles of the author were to ensure simplicity in the architecture and to keep computational costs bounded (the model was originally trained with a single GPU).