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Documentation Index

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The model package provides composable neural network models — MLP and LSTM — built from layer primitives. Each model embeds Model, which manages a slice of layers and exposes a unified parameter and gradient interface consumed by optimizers.

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Layer interface

Every element in Model.Layers must satisfy the Layer interface. The built-in layer types (LinearT, RNNT, LSTMT) all implement it. 
type Layer interface {
    First(x ...*variable.Variable) *variable.Variable
    Forward(x ...*variable.Variable) []*variable.Variable
    Params() layer.Parameters
    Cleargrads()
}
​
First
func(x ...*variable.Variable) *variable.Variable
Runs the layer forward and returns the first output variable. Convenience wrapper around Forward.
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Forward
func(x ...*variable.Variable) []*variable.Variable
Runs the layer forward and returns all output variables.
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Params
func() layer.Parameters
Returns the learnable parameters (layer.Parameters) for this layer.
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Cleargrads
func()
Sets all parameter gradients to nil, preparing for the next forward/backward pass.

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Model

Model is the base struct embedded by MLP and LSTM. It aggregates parameters and gradient clearing across all its layers. 
type Model struct {
    Layers []Layer
}
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Layers
[]Layer
The ordered list of layers that make up the model. You can inspect or replace layers directly.

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Methods

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Params

func (m Model) Params() layer.Parameters
Returns a merged layer.Parameters map from every layer. Keys are prefixed with the layer index ("0.W", "1.b", etc.) so parameter names remain unique across layers.

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Cleargrads

func (m *Model) Cleargrads()
Calls Cleargrads() on every layer, zeroing all gradient tensors. Call this before each backward pass to prevent gradient accumulation.

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Activation

Activation is the function type used for inter-layer activations in MLP. 
type Activation func(x ...*variable.Variable) *variable.Variable
Any function with this signature can be used as an activation. The standard library activations (F.Sigmoid, F.ReLU, F.Tanh, F.Softmax(axis)) all satisfy this type.

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MLP

MLP is a multi-layer perceptron with a configurable number of hidden layers and a shared activation function applied between each layer. The final layer has no activation. 
type MLP struct {
    Activation Activation
    Model
}
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Activation
Activation
The activation function applied after every layer except the last. Defaults to F.Sigmoid.

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NewMLP

func NewMLP(outSize []int, opts ...MLPOptionFunc) *MLP
Creates an MLP where each element of outSize defines the output size of a Linear layer.
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outSize
[]int
required
Output sizes for each layer. len(outSize) determines the depth of the network.
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opts
...MLPOptionFunc
Option functions that customize the MLP before the layers are initialized.
Layer weights are initialized with the default random source. Use WithMLPSource to set a deterministic source for reproducible experiments.

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Option functions

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WithMLPActivation

func WithMLPActivation(activation Activation) MLPOptionFunc
Overrides the default F.Sigmoid activation with any Activation-compatible function.

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WithMLPSource

func WithMLPSource(s randv2.Source) MLPOptionFunc
Sets the random source (math/rand/v2.Source) used to initialize layer weights. Pass a seeded source for reproducible results.

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Forward

func (m *MLP) Forward(x *variable.Variable) *variable.Variable
Runs the input x through every hidden layer with the configured activation, then through the final layer with no activation.
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x
*variable.Variable
required
The input variable. Shape must be compatible with the first layer’s weight matrix.

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LSTM

LSTM wraps a single layer.LSTMT followed by a layer.LinearT projection. It exposes a stateful forward pass and a method to reset the hidden and cell states between sequences. 
type LSTM struct {
    Model
}

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NewLSTM

func NewLSTM(hiddenSize, outSize int, opts ...LSTMOptionFunc) *LSTM
​
hiddenSize
int
required
The dimensionality of the LSTM hidden state.
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outSize
int
required
The output size of the projection Linear layer that follows the LSTM.
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opts
...LSTMOptionFunc
Option functions applied before the layers are constructed.

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Option functions

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WithLSTMSource

func WithLSTMSource(s randv2.Source) LSTMOptionFunc
Sets the random source (math/rand/v2.Source) for initializing both the LSTM and projection layer weights.

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Forward

func (m *LSTM) Forward(x *variable.Variable) *variable.Variable
Runs x through the LSTM layer, then through the projection layer. The LSTM hidden and cell states are carried forward across calls — reset them with ResetState between sequences.

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ResetState

func (m *LSTM) ResetState()
Clears the LSTM hidden state (h) and cell state (c). Call this at the start of each new sequence during training or inference.

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Examples

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Training an MLP

package main

import (
    "fmt"

    F "github.com/itsubaki/autograd/function"
    "github.com/itsubaki/autograd/model"
    "github.com/itsubaki/autograd/optimizer"
    "github.com/itsubaki/autograd/variable"
)

func main() {
    // Two hidden layers of size 10, output size 1
    mlp := model.NewMLP([]int{10, 10, 1})

    opt := &optimizer.SGD{LearningRate: 0.01}

    x := variable.New(1.0, 2.0, 3.0)
    t := variable.New(0.0, 1.0, 0.0)

    for i := range 100 {
        y := mlp.Forward(x)
        loss := F.MeanSquaredError(y, t)

        mlp.Cleargrads()
        loss.Backward()
        opt.Update(mlp)

        if i%10 == 0 {
            fmt.Println("loss:", loss.Data)
        }
    }
}

​
Using ReLU activation

mlp := model.NewMLP(
    []int{64, 64, 10},
    model.WithMLPActivation(F.ReLU),
)

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Training an LSTM on a sequence

lstm := model.NewLSTM(64, 1)
opt := &optimizer.Adam{Alpha: 0.001, Beta1: 0.9, Beta2: 0.999}

for epoch := range 10 {
    lstm.ResetState()
    lstm.Cleargrads()

    var loss *variable.Variable
    for _, x := range sequence {
        y := lstm.Forward(x)
        loss = F.MeanSquaredError(y, target)
    }

    loss.Backward()
    opt.Update(lstm)
}
Call ResetState() at the start of each new sequence so the LSTM does not carry state from the previous sequence into the next.

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See also

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