Deep Learning with torch and mlr3.

remotes::install_github("mlr-org/mlr3torch")

mlr3torch is currently still unstable but under active development. Not everything might work yet and the API might change without notice.

mlr3torch is a deep learning framework for the mlr3 ecosystem built on top of torch. It allows to easily build, train and evaluate deep learning models in a few lines of codes, without needing to worry about low-level details. Off-the-shelf learners are readily available, but custom architectures can be defined by connection PipeOpTorch operators in an mlr3pipelines::Graph.

Using predefined learners such as a simple multi layer perceptron (MLP) works just like any other mlr3 Learner.

library(mlr3torch)
learner_mlp = lrn("classif.mlp",
  # defining network parameters
  activation     = nn_relu,
  layers         = 1,
  d_hidden       = 20,
  # training parameters
  batch_size     = 16,
  epochs         = 50,
  device         = "cpu",
  # Defining the optimizer, loss, and callbacks
  optimizer      = t_opt("adam", lr = 0.1),
  loss           = t_loss("cross_entropy"),
  callbacks      = t_clbk("history"), # this saves the history in the learner
  # Measures to track
  measures_valid = msrs(c("classif.logloss", "classif.ce")),
  measures_train = msrs(c("classif.acc"))
)

This learner can for example be used for resampling or benchmarking.

resample(
  task       = tsk("iris"),
  learner    = learner_mlp,
  resampling = rsmp("holdout")
)
#> <ResampleResult> with 1 resampling iterations
#>  task_id  learner_id resampling_id iteration warnings errors
#>     iris classif.mlp       holdout         1        0      0

Below, we construct the same architecture using PipeOpTorch objects. The first pipeop – a PipeOpTorchIngress – defines the entrypoint of the network. All subsequent pipeops define the neural network layers.

architecture = po("torch_ingress_num") %>>%
  po("nn_linear", out_features = 20) %>>%
  po("nn_relu") %>>%
  po("nn_head")

To turn this into a learner, we configure the loss, optimizer, callbacks and the training arguments.

graph_mlp = architecture %>>%
  po("torch_loss", loss = t_loss("cross_entropy")) %>>%
  po("torch_optimizer", optimizer = t_opt("adam", lr = 0.1)) %>>%
  po("torch_callbacks", callbacks = t_clbk("history")) %>>%
  po("torch_model_classif", batch_size = 16, epochs = 50, device = "cpu")

graph_mlp
#> Graph with 8 PipeOps:
#>                   ID         State            sccssors         prdcssors
#>               <char>        <char>              <char>            <char>
#>    torch_ingress_num <<UNTRAINED>>           nn_linear                  
#>            nn_linear <<UNTRAINED>>             nn_relu torch_ingress_num
#>              nn_relu <<UNTRAINED>>             nn_head         nn_linear
#>              nn_head <<UNTRAINED>>          torch_loss           nn_relu
#>           torch_loss <<UNTRAINED>>     torch_optimizer           nn_head
#>      torch_optimizer <<UNTRAINED>>     torch_callbacks        torch_loss
#>      torch_callbacks <<UNTRAINED>> torch_model_classif   torch_optimizer
#>  torch_model_classif <<UNTRAINED>>                       torch_callbacks

• Off-the-shelf architectures are readily available as mlr3::Learners.
• Custom learners can be defined using the Graph language from mlr3pipelines or using nn_modules.
• The package supports tabular and image data.
• It is possible to customize the training process via (predefined or custom) callbacks.
• The package is fully integrated into the mlr3 ecosystem.

The easiest way to learn about mlr3torch is to read one of the vignettes.

• Without the great R package torch none of this would have been possible.
• The names for the callback stages are taken from luz, another high-level deep learning framework for R torch.
• Building neural networks using PipeOpTorch operators is inspired by keras.

mlr3torch is a free and open source software project that encourages participation and feedback. If you have any issues, questions, suggestions or feedback, please do not hesitate to open an “issue” about it on the GitHub page!

In case of problems / bugs, it is often helpful if you provide a “minimum working example” that showcases the behaviour (but don’t worry about this if the bug is obvious).

Please understand that the resources of the project are limited: response may sometimes be delayed by a few days, and some feature suggestions may be rejected if they are deemed too tangential to the vision behind the project.