In machine learning, a hyperparameter is a parameter whose value is used to control learning process, and HPO is the problem of choosing a set of optimal hyperparameters for a learning algorithm.

**Fishr** is a learning scheme to enforce domain invariance in the space of the gradients of the loss function: specifically, it introduces a regularization term that matches the domain-level variances of gradients across training domains. Critically, the strategy exhibits close relations with the Fisher Information and the Hessian of the loss. Forcing domain-level gradient covariances to be similar during the learning procedure eventually aligns the domain-level loss landscapes locally around the final weights.

Fishr

Fishr: Invariant Gradient Variances for Out-of-Distribution Generalization

Algorithms for Hyper-Parameter Optimization

**rnnDrop** is a [dropout](https://paperswithcode.com/method/dropout) based regularization technique for [recurrent neural networks](https://paperswithcode.com/methods/category/recurrent-neural-networks). It amounts to using the same dropout mask at every timestep. It drops both the non-recurrent and recurrent connections. A simple figure to explain the idea is shown to the right. The figure shows an RNN being trained with rnnDrop for three frames $\left(t-1, t, t+1\right)$ on two different training sequences in the data (denoted as ‘sequence1’ and ‘sequence2’). The black circles denote the randomly omitted hidden nodes during training, and the dotted arrows stand for the model weights connected to those omitted nodes.

*From: RnnDrop: A Novel Dropout for RNNs in ASR by Moon et al*

Source	Algorithms for Hyper-Parameter Optimization
Year	2000
Data Source	CC BY-SA - https://paperswithcode.com