This rule raises an issue when a PyTorch model state is loaded and `torch.nn.Module.eval()` or `torch.nn.Module.train()` is not called.

== Why is this an issue?

When using PyTorch it is common practice to load and save a model's state from/to a `.pth` file.
Doing so allows, for example, to instantiate an untrained model and load learned parameters coming from another pre-trained model.
Once the learned parameters are loaded to the model it is important, before inferencing, 
to clearly state the intention by calling `torch.nn.Module.eval()` method to set the model in evaluation mode
or calling `torch.nn.Module.train()` to indicate the training will resume. 
Failing to call `torch.nn.Module.eval()` would leave the model in training mode which may not be the intention.

== How to fix it

Call the `torch.nn.Module.eval()` or `torch.nn.Module.train()` method on the model.

=== Code examples

==== Noncompliant code example

[source,python,diff-id=1,diff-type=noncompliant]
----
import torch
import torchvision.models as models

model = models.vgg16()
model.load_state_dict(torch.load('model_weights.pth')) # Noncompliant: model.train() or model.eval() was not called.
----

==== Compliant solution

[source,python,diff-id=1,diff-type=compliant]
----
import torch
import torchvision.models as models

model = models.vgg16()
model.load_state_dict(torch.load('model_weights.pth')) 
model.eval()
----
== Resources
=== Documentation

* PyTorch Documentation - https://pytorch.org/docs/master/generated/torch.nn.Module.html#torch.nn.Module.eval[eval - reference]
* PyTorch Documentation - https://pytorch.org/docs/master/generated/torch.nn.Module.html#torch.nn.Module.train[train - reference]
* PyTorch Documentation - https://pytorch.org/docs/stable/notes/autograd.html#evaluation-mode-nn-module-eval[Autograd - Evaluation Mode]

ifdef::env-github,rspecator-view[]

(visible only on this page)

== Implementation specification 


=== Message 

Primary : Set the module in training or evaluation mode.


=== Issue location

Primary : the call to model.load_state_dict


=== Quickfix

No

endif::env-github,rspecator-view[]