The Elements of Differentiable Programming

Notation

Table 1: Naming conventions

Notation Description
X⊆RD\cX \subseteq \RR^D Input space (e.g., features)
Y⊆RM\cY \subseteq \RR^M Output space (e.g., classes)
Sk⊆RDk\cS_k \subseteq \RR^{D_k} Output space on layer or state kk
W⊆RP\cW \subseteq \RR^P Weight space
Λ⊆RQ\Lambda \subseteq \RR^Q Hyperparameter space
Θ⊆RR\Theta \subseteq \RR^R Distribution parameter space, logit space
NN Number of training samples
TT Number of optimization iterations
x∈X\x \in \cX Input vector
y∈Y\y \in \cY Target vector
sk∈Sk\s_k \in \cS_k State vector kk
w∈W\w \in \cW Network (model) weights
λ∈Λ\lambdav \in \Lambda Hyperparameters
θ∈Θ\thetav \in \Theta Distribution parameters, logits
π∈[0,1]\pi \in [0,1] Probability value
π∈△M\piv \in \triangle^M Probability vector

Table 2: Naming conventions (continued)

Notation Description
ff Network function
f(⋅;x)f(\cdot; \x) Network function with x\x fixed
LL Objective function
ℓ\ell Loss function
κ\kappa Kernel function
ϕ\phi Output embedding, sufficient statistic
step\mathrm{step} Heaviside step function
logisticσ\logistic_\sigma Logistic function with temperature σ\sigma
logistic\logistic Shorthand for logistic1\logistic_1
pθp_\thetav Model distribution with parameters θ\thetav
ρ\rho Data distribution over X×Y\cX \times \cY
ρX\rho_\cX Data distribution over X\cX
μ,σ2\muv, \sigma^2 Mean and variance
ZZ Random noise variable