mlr_pipeops_module: Class for Torch Module Wrappers

In mlr3torch: Deep Learning with 'mlr3'

Class for Torch Module Wrappers

Description

PipeOpModule wraps an nn_module or function that is being called during the train phase of this mlr3pipelines::PipeOp. By doing so, this allows to assemble PipeOpModules in a computational mlr3pipelines::Graph that represents either a neural network or a preprocessing graph of a lazy_tensor. In most cases it is easier to create such a network by creating a graph that generates this graph.

In most cases it is easier to create such a network by creating a structurally related graph consisting of nodes of class PipeOpTorchIngress and PipeOpTorch. This graph will then generate the graph consisting of PipeOpModules as part of the ModelDescriptor.

Input and Output Channels

The number and names of the input and output channels can be set during construction. They input and output "torch_tensor" during training, and NULL during prediction as the prediction phase currently serves no meaningful purpose.

State

The state is the value calculated by the public method shapes_out().

Parameters

No parameters.

Internals

During training, the wrapped nn_module / function is called with the provided inputs in the order in which the channels are defined. Arguments are not matched by name.

Super class

mlr3pipelines::PipeOp -> PipeOpModule

Public fields

module

(nn_module)
The torch module that is called during the training phase.

Methods

Public methods

• PipeOpModule$new()

• PipeOpModule$clone()

Inherited methods

• mlr3pipelines::PipeOp$help()
• mlr3pipelines::PipeOp$predict()
• mlr3pipelines::PipeOp$print()
• mlr3pipelines::PipeOp$train()

---

Method new()

Creates a new instance of this R6 class.

Usage

PipeOpModule$new(
  id = "module",
  module = nn_identity(),
  inname = "input",
  outname = "output",
  param_vals = list(),
  packages = character(0)
)

Arguments

id

(character(1))
The id for of the new object.

module

(nn_module or ⁠function()⁠)
The torch module or function that is being wrapped.

inname

(character())
The names of the input channels.

outname

(character())
The names of the output channels. If this parameter has length 1, the parameter module must return a tensor. Otherwise it must return a list() of tensors of corresponding length.

param_vals

(named list())
Parameter values to be set after construction.

packages

(character())
The R packages this object depends on.

---

Method clone()

The objects of this class are cloneable with this method.

Usage

PipeOpModule$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

See Also

Other Graph Network: ModelDescriptor(), TorchIngressToken(), mlr_learners_torch_model, mlr_pipeops_torch, mlr_pipeops_torch_ingress, mlr_pipeops_torch_ingress_categ, mlr_pipeops_torch_ingress_ltnsr, mlr_pipeops_torch_ingress_num, model_descriptor_to_learner(), model_descriptor_to_module(), model_descriptor_union(), nn_graph()

Other PipeOp: mlr_pipeops_torch_callbacks, mlr_pipeops_torch_optimizer

Examples

## creating an PipeOpModule manually

# one input and output channel
po_module = po("module",
  id = "linear",
  module = torch::nn_linear(10, 20),
  inname = "input",
  outname = "output"
)
x = torch::torch_randn(16, 10)
# This calls the forward function of the wrapped module.
y = po_module$train(list(input = x))
str(y)

# multiple input and output channels
nn_custom = torch::nn_module("nn_custom",
  initialize = function(in_features, out_features) {
    self$lin1 = torch::nn_linear(in_features, out_features)
    self$lin2 = torch::nn_linear(in_features, out_features)
  },
  forward = function(x, z) {
    list(out1 = self$lin1(x), out2 = torch::nnf_relu(self$lin2(z)))
  }
)

module = nn_custom(3, 2)
po_module = po("module",
  id = "custom",
  module = module,
  inname = c("x", "z"),
  outname = c("out1", "out2")
)
x = torch::torch_randn(1, 3)
z = torch::torch_randn(1, 3)
out = po_module$train(list(x = x, z = z))
str(out)

# How such a PipeOpModule is usually generated
graph = po("torch_ingress_num") %>>% po("nn_linear", out_features = 10L)
result = graph$train(tsk("iris"))
# The PipeOpTorchLinear generates a PipeOpModule and adds it to a new (module) graph
result[[1]]$graph
linear_module = result[[1L]]$graph$pipeops$nn_linear
linear_module
formalArgs(linear_module$module)
linear_module$input$name

# Constructing a PipeOpModule using a simple function
po_add1 = po("module",
  id = "add_one",
  module = function(x) x + 1
)
input = list(torch_tensor(1))
po_add1$train(input)$output

mlr3torch documentation built on Aug. 26, 2025, 5:09 p.m.