`Boltz.Layers` API Reference

julia

ClassTokens(dim; init=zeros32)

Appends class tokens to an input with embedding dimension dim for use in many vision transformer models.

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Boltz.Layers.ConvNormActivation Type

julia

ConvNormActivation(kernel_size::Dims, in_chs::Integer, hidden_chs::Dims{N},
    activation; norm_layer=nothing, conv_kwargs=(;), norm_kwargs=(;),
    last_layer_activation::Bool=false) where {N}

Construct a Chain of convolutional layers with normalization and activation functions.

Arguments

kernel_size: size of the convolutional kernel
in_chs: number of input channels
hidden_chs: dimensions of the hidden layers
activation: activation function

Keyword Arguments

norm_layer: Function with signature f(i::Integer, dims::Integer, act::F; kwargs...). i is the location of the layer in the model, dims is the channel dimension of the input, and act is the activation function. kwargs are forwarded from the norm_kwargs input, The function should return a normalization layer. Defaults to nothing, which means no normalization layer is used
conv_kwargs: keyword arguments for the convolutional layers
norm_kwargs: keyword arguments for the normalization layers
last_layer_activation: set to true to apply the activation function to the last layer

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Boltz.Layers.DynamicExpressionsLayer Type

julia

DynamicExpressionsLayer(operator_enum::OperatorEnum, expressions::Node...;
    eval_options::EvalOptions=EvalOptions())
DynamicExpressionsLayer(operator_enum::OperatorEnum,
    expressions::AbstractVector{<:Node}; kwargs...)

Wraps a DynamicExpressions.jl Node into a Lux layer and allows the constant nodes to be updated using any of the AD Backends.

For details about these expressions, refer to the DynamicExpressions.jl documentation.

Arguments

operator_enum: OperatorEnum from DynamicExpressions.jl
expressions: Node from DynamicExpressions.jl or AbstractVector{<:Node}

Keyword Arguments

turbo: Use LoopVectorization.jl for faster evaluation (Deprecated)
bumper: Use Bumper.jl for faster evaluation (Deprecated)
eval_options: EvalOptions from DynamicExpressions.jl

These options are simply forwarded to DynamicExpressions.jl's eval_tree_array and eval_grad_tree_array function.

Extended Help

Example

julia

julia> operators = OperatorEnum(; binary_operators=[+, -, *], unary_operators=[cos]);

julia> x1 = Node(; feature=1);

julia> x2 = Node(; feature=2);

julia> expr_1 = x1 * cos(x2 - 3.2)
x1 * cos(x2 - 3.2)

julia> expr_2 = x2 - x1 * x2 + 2.5 - 1.0 * x1
((x2 - (x1 * x2)) + 2.5) - (1.0 * x1)

julia> layer = Layers.DynamicExpressionsLayer(operators, expr_1, expr_2);

julia> ps, st = Lux.setup(Random.default_rng(), layer)
((layer_1 = (layer_1 = (params = Float32[3.2],), layer_2 = (params = Float32[2.5, 1.0],)), layer_2 = NamedTuple()), (layer_1 = (layer_1 = NamedTuple(), layer_2 = NamedTuple()), layer_2 = NamedTuple()))

julia> x = [1.0f0 2.0f0 3.0f0
            4.0f0 5.0f0 6.0f0]
2×3 Matrix{Float32}:
 1.0  2.0  3.0
 4.0  5.0  6.0

julia> layer(x, ps, st)[1] ≈ Float32[0.6967068 -0.4544041 -2.8266668; 1.5 -4.5 -12.5]
true

julia> ∂x, ∂ps, _ = Zygote.gradient(Base.Fix1(sum, abs2) ∘ first ∘ layer, x, ps, st);

julia> ∂x ≈ Float32[-14.0292 54.206482 180.32669; -0.9995737 10.7700815 55.6814]
true

julia> ∂ps.layer_1.layer_1.params ≈ Float32[-6.451908]
true

julia> ∂ps.layer_1.layer_2.params ≈ Float32[-31.0, 90.0]
true

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Boltz.Layers.HamiltonianNN Type

julia

HamiltonianNN{FST}(model; autodiff=nothing) where {FST}

Constructs a Hamiltonian Neural Network [1]. This neural network is useful for learning symmetries and conservation laws by supervision on the gradients of the trajectories. It takes as input a concatenated vector of length 2n containing the position (of size n) and momentum (of size n) of the particles. It then returns the time derivatives for position and momentum.

Arguments

FST: If true, then the type of the state returned by the model must be same as the type of the input state. See the documentation on StatefulLuxLayer for more information.
model: A Lux.AbstractLuxLayer neural network that returns the Hamiltonian of the system. The model must return a "batched scalar", i.e. all the dimensions of the output except the last one must be equal to 1. The last dimension must be equal to the batchsize of the input.

Keyword Arguments

autodiff: The autodiff framework to be used for the internal Hamiltonian computation. The default is nothing, which selects the best possible backend available. The available options are AutoForwardDiff and AutoZygote.

Autodiff Backends

`autodiff`	Package Needed	Notes
`AutoZygote`	`Zygote.jl`	Preferred Backend. Chosen if `Zygote` is loaded and `autodiff` is `nothing`.
`AutoForwardDiff`		Chosen if `Zygote` is not loaded and `autodiff` is `nothing`.

Note

This layer uses nested autodiff. Please refer to the manual entry on Nested Autodiff for more information and known limitations.

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Boltz.Layers.MLP Type

julia

MLP(in_dims::Integer, hidden_dims::Dims{N}, activation=NNlib.relu; norm_layer=nothing,
    dropout_rate::Real=0.0f0, dense_kwargs=(;), norm_kwargs=(;),
    last_layer_activation=false) where {N}

Construct a multi-layer perceptron (MLP) with dense layers, optional normalization layers, and dropout.

Arguments

in_dims: number of input dimensions
hidden_dims: dimensions of the hidden layers
activation: activation function (stacked after the normalization layer, if present else after the dense layer)

Keyword Arguments

norm_layer: Function with signature f(i::Integer, dims::Integer, act::F; kwargs...). i is the location of the layer in the model, dims is the channel dimension of the input, and act is the activation function. kwargs are forwarded from the norm_kwargs input, The function should return a normalization layer. Defaults to nothing, which means no normalization layer is used
dropout_rate: dropout rate (default: 0.0f0)
dense_kwargs: keyword arguments for the dense layers
norm_kwargs: keyword arguments for the normalization layers
last_layer_activation: set to true to apply the activation function to the last layer

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Boltz.Layers.MultiHeadSelfAttention Type

julia

MultiHeadSelfAttention(in_planes::Int, number_heads::Int; use_qkv_bias::Bool=false,
    attention_dropout_rate::T=0.0f0, projection_dropout_rate::T=0.0f0)

Multi-head self-attention layer

Arguments

planes: number of input channels
nheads: number of heads
use_qkv_bias: whether to use bias in the layer to get the query, key and value
attn_dropout_prob: dropout probability after the self-attention layer
proj_dropout_prob: dropout probability after the projection layer

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Boltz.Layers.PatchEmbedding Type

julia

PatchEmbedding(image_size, patch_size, in_channels, embed_planes;
    norm_layer=Returns(Lux.NoOpLayer()), flatten=true)

Constructs a patch embedding layer with the given image size, patch size, input channels, and embedding planes. The patch size must be a divisor of the image size.

Arguments

image_size: image size as a tuple
patch_size: patch size as a tuple
in_channels: number of input channels
embed_planes: number of embedding planes

Keyword Arguments

norm_layer: Takes the embedding planes as input and returns a layer that normalizes the embedding planes. Defaults to no normalization.
flatten: set to true to flatten the output of the convolutional layer

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Boltz.Layers.PeriodicEmbedding Type

julia

PeriodicEmbedding(idxs, periods)

Create an embedding periodic in some inputs with specified periods. Input indices not in idxs are passed through unchanged, but inputs in idxs are moved to the end of the output and replaced with their sines, followed by their cosines (scaled appropriately to have the specified periods). This smooth embedding preserves phase information and enforces periodicity.

For example, layer = PeriodicEmbedding([2, 3], [3.0, 1.0]) will create a layer periodic in the second input with period 3.0 and periodic in the third input with period 1.0. In this case, layer([a, b, c, d], st) == ([a, d, sinpi(2 / 3.0 * b), sinpi(2 / 1.0 * c), cospi(2 / 3.0 * b), cospi(2 / 1.0 * c)], st).

Arguments

idxs: Indices of the periodic inputs
periods: Periods of the periodic inputs, in the same order as in idxs

Inputs

x must be an AbstractArray with issubset(idxs, axes(x, 1))
st must be a NamedTuple where st.k = 2 ./ periods, but on the same device as x

Returns

AbstractArray of size (size(x, 1) + length(idxs), ...) where ... are the other dimensions of x.
st, unchanged

Example

julia

julia> layer = Layers.PeriodicEmbedding([2], [4.0])
PeriodicEmbedding([2], [4.0])

julia> ps, st = Lux.setup(Random.default_rng(), layer);

julia> all(layer([1.1, 2.2, 3.3], ps, st)[1] .==
           [1.1, 3.3, sinpi(2 / 4.0 * 2.2), cospi(2 / 4.0 * 2.2)])
true

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Boltz.Layers.PositiveDefinite Type

julia

PositiveDefinite(model, x0; ψ, r)
PositiveDefinite(model; in_dims, ψ, r)

Constructs a Lyapunov-Net [2], which is positive definite about x0 whenever ψ and r meet certain conditions described below.

For a model ϕ, PositiveDefinite(ϕ, ψ, r, x0)(x, ps, st) = ψ(ϕ(x, ps, st) - ϕ(x0, ps, st)) + r(x, x0). This results in a model which maps x0 to 0 and any other input to a positive number (i.e., a model which is positive definite about x0) whenever ψ is positive definite about zero and r returns a positive number for any non-equal inputs and zero for equal inputs.

Arguments

model: the underlying model being transformed into a positive definite function
x0: The unique input that will be mapped to zero instead of a positive number

Keyword Arguments

in_dims: the number of input dimensions if x0 is not provided; uses x0 = zeros(in_dims)
ψ: a positive definite function (about zero); defaults to $ψ (x) = | | x | |^{2}$
r: a bivariate function such that r(x0, x0) = 0 and r(x, x0) > 0 whenever x ≠ x0; defaults to $r (x, y) = | | x - y | |^{2}$

Inputs

x: will be passed directly into model, so must meet the input requirements of that argument

Returns

The output of the positive definite model
The state of the positive definite model. If the underlying model changes it state, the state will be updated first according to the call with the input x0, then according to the call with the input x.

States

st: a NamedTuple containing the state of the underlying model and the x0 value

Parameters

Same as the underlying model

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Boltz.Layers.ShiftTo Type

julia

ShiftTo(model, in_val, out_val)

Vertically shifts the output of model to output out_val when the input is in_val.

For a model ϕ, ShiftTo(ϕ, in_val, out_val)(x, ps, st) = ϕ(x, ps, st) + Δϕ, where Δϕ = out_val - ϕ(in_val, ps, st).

Arguments

model: the underlying model being transformed into a positive definite function
in_val: The input that will be mapped to out_val
out_val: The value that the output will be shifted to when the input is in_val

Inputs

x: will be passed directly into model, so must meet the input requirements of that argument

Returns

The output of the shifted model
The state of the shifted model. If the underlying model changes it state, the state will be updated first according to the call with the input in_val, then according to the call with the input x.

States

st: a NamedTuple containing the state of the underlying model and the in_val and out_val values

Parameters

Same as the underlying model

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Boltz.Layers.SplineLayer Type

julia

SplineLayer(in_dims, grid_min, grid_max, grid_step, basis::Type{Basis};
    train_grid::Union{Val, Bool}=Val(false), init_saved_points=nothing)

Constructs a spline layer with the given basis function.

Arguments

in_dims: input dimensions of the layer. This must be a tuple of integers, to construct a flat vector of saved_points pass in ().
grid_min: minimum value of the grid.
grid_max: maximum value of the grid.
grid_step: step size of the grid.
basis: basis function to use for the interpolation. Currently only the basis functions from DataInterpolations.jl are supported:
1. ConstantInterpolation
2. LinearInterpolation
3. QuadraticInterpolation
4. QuadraticSpline
5. CubicSpline

Keyword Arguments

train_grid: whether to train the grid or not.
init_saved_points: values of the function at multiples of the time step. Initialized by default to a random vector sampled from the unit normal. Alternatively, can take a function with the signature init_saved_points(rng, in_dims, grid_min, grid_max, grid_step).

Warning

Currently this layer is limited since it relies on DataInterpolations.jl which doesn't work with GPU arrays. This will be fixed in the future by extending support to different basis functions.

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Boltz.Layers.TensorProductLayer Type

julia

TensorProductLayer(basis_fns, out_dim::Int; init_weight = randn32)

Constructs the Tensor Product Layer, which takes as input an array of n tensor product basis, $[B_{1}, B_{2}, \dots, B_{n}]$ a data point x, computes

z_{i} = W_{i, :} ⊙ [B_{1} (x_{1}) \otimes B_{2} (x_{2}) \otimes \dots \otimes B_{n} (x_{n})]

where $W$ is the layer's weight, and returns $[z_{1}, \dots, z_{o u t}]$ .

Arguments

basis_fns: Array of TensorProductBasis $[B_{1} (n_{1}), \dots, B_{k} (n_{k})]$ , where $k$ corresponds to the dimension of the input.
out_dim: Dimension of the output.

Keyword Arguments

init_weight: Initializer for the weight matrix. Defaults to randn32.

Limited Backend Support

Support for backends apart from CPU and CUDA is limited and slow due to limited support for kron in the backend.

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Boltz.Layers.ViPosEmbedding Type

julia

ViPosEmbedding(embedding_size, number_patches; init = randn32)

Positional embedding layer used by many vision transformer-like models.

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Boltz.Layers.VisionTransformerEncoder Type

julia

VisionTransformerEncoder(in_planes, depth, number_heads; mlp_ratio = 4.0f0,
    dropout = 0.0f0)

Transformer as used in the base ViT architecture [3].

Arguments

in_planes: number of input channels
depth: number of attention blocks
number_heads: number of attention heads

Keyword Arguments

mlp_ratio: ratio of MLP layers to the number of input channels
dropout_rate: dropout rate

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Boltz.Layers.ConvBatchNormActivation Method

julia

ConvBatchNormActivation(kernel_size::Dims, (in_filters, out_filters)::Pair{Int, Int},
    depth::Int, act::F; use_norm::Bool=true, conv_kwargs=(;),
    last_layer_activation::Bool=true, norm_kwargs=(;)) where {F}

This function is a convenience wrapper around ConvNormActivation that constructs a chain with norm_layer set to Lux.BatchNorm if use_norm is true and nothing otherwise. In most cases, users should use ConvNormActivation directly for a more flexible interface.

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Boltz.Layers API Reference ​

`Boltz.Layers` API Reference