more docstrings

src/optimise/optimisers.jl

@@ -7,23 +7,20 @@ const ϵ = 1e-8
 # TODO: should use weak refs
 
 """
-# Descent
+  Descent(η)
 
 ## Description
 Classic gradient descent optimiser with learning rate `η`.
 For each parameter `p` and its gradient `δp`, this runs `p -= η*δp`
 
-## Constructors
-  - `Descent()`: Use the default learning rate (η), as described in the parameters section.
-
-  - `Descent(η)`: Provide a custom learning rate (η) to the Descent optimiser.
-
 ## Parameters
-  - Learning rate (η): The amount by which the gradients are discounted before updating the weights. Defaults to `0.1`.
+  - Learning Rate (η): The amount by which the gradients are discounted before updating the weights. Defaults to `0.1`.
 
 ## Example
 ```julia-repl
-opt = Descent()
+opt = Descent() # uses default η (0.1)
+
+opt = Descent(0.3) # use provided η
 
 ps = params(model)
 
@@ -47,11 +44,18 @@ end
 """
     Momentum(η, ρ)
 
-    Calls to `Momentum()` default to:
-      - learning rate (η): 0.01
-      - decay (ρ): 0.9
-
 Gradient descent with learning rate `η` and momentum `ρ`.
+
+## Parameters
+  - Learning Rate (`η`): Amount by which gradients are discounted before updating the weights. Defaults to `0.01`.
+  - Momentum (`ρ`): Parameter that accelerates descent in the relevant direction and dampens oscillations. Defaults to `0.9`.
+
+## Examples
+```julia
+opt = Momentum() # uses defaults of η = 0.01 and ρ = 0.9
+
+opt = Momentum(0.01, 0.99)
+```
 """
 mutable struct Momentum
   eta::Float64
@@ -71,11 +75,18 @@ end
 """
     Nesterov(η, ρ)
 
-    Calls to `Nesterov()` default to:
-      - learning rate (η): 0.001
-      - nesterov momentum (ρ): 0.9
-
 Gradient descent with learning rate  `η` and Nesterov momentum `ρ`.
+
+## Parameters
+  - Learning Rate (η): Amount by which the gradients are dicsounted berfore updating the weights. Defaults to `0.001`.
+  - Nesterov Momentum (ρ): Paramters controlling the amount of nesterov momentum to be applied. Defaults to `0.9`.
+
+## Examples
+```julia
+opt = Nesterov() # uses defaults η = 0.001 and ρ = 0.9
+
+opt = Nesterov(0.003, 0.95)
+```
 """
 mutable struct Nesterov
   eta::Float64
@@ -96,13 +107,21 @@ end
 """
     RMSProp(η, ρ)
 
-    Calls to `RMSProp()` default to:
+Implements the RMSProp algortihm. Often a good choice for recurrent networks. Paramters other than learning rate generally don't need tuning.
-      - learning rate (η): 0.001
-      - rho (ρ): 0.9
 
+## Parameters
+  - Learning Rate (η): Defaults to `0.001`.
+  - Rho (ρ): Defaults to `0.9`.
+
+## Examples
+```julia
+opt = RMSProp() # uses default η = 0.001 and ρ = 0.9
+
+opt = RMSProp(0.002, 0.95)
+```
+
+## References
 [RMSProp](https://www.cs.toronto.edu/~tijmen/csc321/slides/lecture_slides_lec6.pdf)
-optimiser. Parameters other than learning rate don't need tuning. Often a good
-choice for recurrent networks.
 """
 mutable struct RMSProp
   eta::Float64
@@ -122,10 +141,20 @@ end
 """
     ADAM(η, β::Tuple)
 
-    Calls to `ADAM()` default to:
+Implements the ADAM optimiser.
-      - learning rate (η): 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
+## Paramters
+  - Learning Rate (`η`): Defaults to `0.001`.
+  - Beta (`β::Tuple`): The first element refers to β1 and the second to β2. Defaults to `(0.9, 0.999)`.
+
+## Examples
+
+```julia
+opt = ADAM() # uses the default η = 0.001 and β = (0.9, 0.999)
+
+opt = ADAM(0.001, (0.9, 0.8))
+```
+## References
 [ADAM](https://arxiv.org/abs/1412.6980v8) optimiser.
 """
 mutable struct ADAM
@@ -149,10 +178,21 @@ end
 """
     RADAM(η, β::Tuple)
 
-    Calls to `RADAM()` default to:
+Implements the rectified ADAM optimizer.
-      - learning rate (η): 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
+## Parameters
+  - Learning Rate (η): Defaults to `0.001`
+  - Beta (β::Tuple): The first element refers to β1 and the second to β2. Defaults to `(0.9, 0.999)`.
+
+## Examples
+
+```julia
+opt = RADAM() # uses the default η = 0.001 and β = (0.9, 0.999)
+
+opt = RADAM(0.001, (0.9, 0.8))
+```
+
+## References
 [RADAM](https://arxiv.org/pdf/1908.03265v1.pdf) optimiser (Rectified ADAM).
 """
 mutable struct RADAM
@@ -183,12 +223,20 @@ end
 """
     AdaMax(η, β::Tuple)
 
-    Calls to `AdaMax()` default to:
+Variant of ADAM based on ∞-norm.
-      - learning rate (η): 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
-[AdaMax](https://arxiv.org/abs/1412.6980v9) optimiser. Variant of ADAM based on
+## Parameters
-the ∞-norm.
+  - Learning Rate (η): Defaults to `0.001`
+  - Beta (β::Tuple): The first element refers to β1 and the second to β2. Defaults to `(0.9, 0.999)`.
+
+## Examples
+```julia
+opt = AdaMax() # uses default η and β	
+
+opt = AdaMax(0.001, (0.9, 0.995))
+```
+## References
+[AdaMax](https://arxiv.org/abs/1412.6980v9) optimiser.
 """
 mutable struct AdaMax
   eta::Float64
@@ -211,9 +259,19 @@ end
 """
     ADAGrad(η)
 
-    Calls to `AdaGrad()` default to:
+Implements AdaGrad. It has parameter specific learning rates based on how frequently it is updated.
-      - learning rate (η): 0.1
 
+## Parameters
+  - Learning Rate (η): Defaults to `0.1`
+
+## Examples
+```julia
+opt = ADAGrad() # uses default η = 0.1
+
+opt = ADAGrad(0.001)
+```
+
+## References
 [ADAGrad](http://www.jmlr.org/papers/volume12/duchi11a/duchi11a.pdf) optimiser.
 Parameters don't need tuning.
 """
@@ -234,11 +292,19 @@ end
 """
     ADADelta(ρ)
 
-    Calls to `ADADelta()` default to:
+Version of ADAGrad that adapts learning rate based on a window of past gradient updates. Parameters don't need tuning.
-      rho (ρ): 0.9
 
-[ADADelta](https://arxiv.org/abs/1212.5701) optimiser. Parameters don't need
+## Parameters
-tuning.
+  - Rho (ρ): Factor by which gradient is decayed at each time step. Defaults to `0.9`.
+
+## Examples
+```julia
+opt = ADADelta() # uses default ρ = 0.9
+opt = ADADelta(0.89)
+```
+
+## References
+[ADADelta](https://arxiv.org/abs/1212.5701) optimiser.
 """
 mutable struct ADADelta
   rho::Float64
@@ -259,12 +325,20 @@ end
 """
     AMSGrad(η, β::Tuple)
 
-    Calls to `AMSGrad()` default to:
+Implements AMSGrad version of the ADAM optimiser. Parameters don't need tuning.
-      - learning rate (η): 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
-[AMSGrad](https://openreview.net/forum?id=ryQu7f-RZ) optimiser. Parameters don't need
+## Parameters
-tuning.
+  - Learning Rate (η): Defaults to `0.001`.
+  - Beta (β::Tuple): The first element refers to β1 and the second to β2. Defaults to `(0.9, 0.999)`.
+
+## Examples
+```julia
+opt = AMSGrad() # uses default η and β
+opt = AMSGrad(0.001, (0.89, 0.995))
+```
+
+## References
+[AMSGrad](https://openreview.net/forum?id=ryQu7f-RZ) optimiser.
 """
 mutable struct AMSGrad
   eta::Float64
@@ -286,12 +360,20 @@ end
 """
     NADAM(η, β::Tuple)
 
-    Calls to `NADAM()` default to:
+Nesterov variant of ADAM. Parameters don't need tuning.
-      - learning rate (η): 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
-[NADAM](http://cs229.stanford.edu/proj2015/054_report.pdf) optimiser. Parameters don't need
+## Parameters
-tuning.
+  - Learning Rate (η): Defaults to `0.001`.
+  - Beta (β::Tuple): The first element refers to β1 and the second to β2. Defaults to `(0.9, 0.999)`.
+
+## Examples
+```julia
+opt = NADAM() # uses default η and β
+opt = NADAM(0.002, (0.89, 0.995))
+```
+
+## References
+[NADAM](http://cs229.stanford.edu/proj2015/054_report.pdf) optimiser.
 """
 mutable struct NADAM
   eta::Float64
@@ -314,11 +396,21 @@ end
 """
     ADAMW(η, β::Tuple, decay)
 
-    Calls to `ADAMW()` default to:
+Variant of ADAM defined by fixing weight decay regularization.
-      - learning rate (η) 0.001
-      - (beta1, beta2) (β): (0.9, 0.999)
 
-[ADAMW](https://arxiv.org/abs/1711.05101) fixing weight decay regularization in Adam.
+## Parameters
+  - Learning Rate (η): Defaults to `0.001`.
+  - Beta (β::Tuple): The first element refers to β1 and the second to β2. Defaults to (0.9, 0.999).
+  - decay: Decay applied to weights during optimisation. Defaults to 0.
+
+## Examples
+```julia
+opt = ADAMW() # uses default η, β and decay
+opt = ADAMW(0.001, (0.89, 0.995), 0.1) 
+```
+
+## References
+[ADAMW](https://arxiv.org/abs/1711.05101)
 """
 ADAMW(η = 0.001, β = (0.9, 0.999), decay = 0) =
   Optimiser(ADAM(η, β), WeightDecay(decay))
@@ -353,10 +445,12 @@ end
 """
   InvDecay(γ)
 
-  Calls to `InvDecay()` default to:
+Applies inverse time decay to an optimiser
-    - gamma (γ): 0.001
 
-Apply inverse time decay to an optimiser
+## Parameters
+  - gamma (γ): Defaults to `0.001`
+
+## Example
 ```julia
   Optimiser(InvDecay(..), Opt(..))
 ```
@@ -379,17 +473,20 @@ end
 """
   ExpDecay(eta, decay, decay_step, clip)
 
-  Calls to `ExpDecay()` default to:
-    - learning rate (eta): 0.001
-    - decay: 0.1
-    - decay_step: 1000
-    - clip: 1e-4
-
 Discount the learning rate `eta` by `decay` every `decay_step` till a minimum of `clip`.
 
+## Parameters
+  - Learning Rate (eta): Defaults to `0.001`.
+  - decay: Factor by which the learning rate is discounted. Defaults to `0.1`.
+  - decay_step: Schedules decay operations by setting number of steps between two decay operations. Defaults to `1000`.
+  - clip: Minimum value of learning rate. Defaults to `1e-4`.
+
+## Example
 To apply exponential decay to an optimiser:
 ```julia
   Optimiser(ExpDecay(..), Opt(..))
+
+  opt = Optimiser(ExpDecay(), ADAM())
 ```
 """
 mutable struct ExpDecay
@@ -415,10 +512,10 @@ end
 """
   WeightDecay(wd)
 
-  Calls to `WeightDecay()` default to:
+Decays the weight by `wd`
-    - weight decay (wd): 0
 
-Decay the weight parameter by `wd`
+## Parameters
+  - weight decay (wd): 0
 """
 mutable struct WeightDecay
   wd::Real