**Randomized Leaky Rectified Linear Units**, or **RReLU**, are an activation function that randomly samples the negative slope for activation values. It was first proposed and used in the Kaggle NDSB Competition. During training, $a\_{ji}$ is a random number sampled from a uniform distribution $U\left(l, u\right)$. Formally:

$$ y\_{ji} = x\_{ji} \text{   if } x\_{ji} \geq{0} $$
$$ y\_{ji} = a\_{ji}x\_{ji} \text{   if } x\_{ji} < 0 $$

where

$$\alpha\_{ji} \sim U\left(l, u\right), l < u \text{ and } l, u \in \left[0,1\right)$$

In the test phase, we take average of all the $a\_{ji}$ in training similar to [dropout](https://paperswithcode.com/method/dropout), and thus set $a\_{ji}$ to $\frac{l+u}{2}$ to get a deterministic result. As suggested by the NDSB competition winner, $a\_{ji}$ is sampled from $U\left(3, 8\right)$. 

At test time, we use:

$$ y\_{ji} = \frac{x\_{ji}}{\frac{l+u}{2}} $$

A **Deactivable Skip Connection** is a type of skip connection which, instead of concatenating the encoder features
(red) and decoder features (blue), as with [standard skip connections](https://paperswithcode.com/methods/category/skip-connections), it instead fuses the encoder features with part of the decoder features (light blue), to be able to deactivate this operation when needed.

Deactivable Skip Connection

Cross-modal Deep Face Normals with Deactivable Skip Connections

RReLU

Empirical Evaluation of Rectified Activations in Convolutional Network

A **Non-Local Block** is an image block module used in neural networks that wraps a [non-local operation](https://paperswithcode.com/method/non-local-operation). We can define a non-local block as:

$$ \mathbb{z}\_{i} = W\_{z}\mathbb{y\_{i}} + \mathbb{x}\_{i} $$

where $y\_{i}$ is the output from the non-local operation and $+ \mathbb{x}\_{i}$ is a [residual connection](https://paperswithcode.com/method/residual-connection).

Source	Empirical Evaluation of Rectified Activations in Convolutional Network
Year	2000
Data Source	CC BY-SA - https://paperswithcode.com