A Non-Local Block is an image block module used in neural networks that wraps a non-local operation. We can define a non-local block as:
z_i=W_zy_i+x_i\mathbb{z}\_{i} = W\_{z}\mathbb{y\_{i}} + \mathbb{x}\_{i}z_i=W_zy_i+x_i
where y_iy\_{i}y_i is the output from the non-local operation and +x_i+ \mathbb{x}\_{i}+x_i is a residual connection.