📚 documentation minor fixes

auto_tutorials_source/Bayesian_Methods/README.txt

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+.. _bayesian_methods_examples:
+
+Bayesian Methods
+-----------------
+
+Tutorials for Bayesian approaches to uncertainty estimation.

auto_tutorials_source/Classification/README.txt

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+.. _Classification_examples:
+
+Classification
+---------------------------
+
+Tutorials for modeling uncertainty in classification tasks.

auto_tutorials_source/Classification/tutorial_bayesian.py

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+"""
+Train a Bayesian Neural Network in Three Minutes
+================================================
+
+In this tutorial, we will train a variational inference Bayesian Neural Network (BNN) LeNet classifier on the MNIST dataset.
+
+Foreword on Bayesian Neural Networks
+------------------------------------
+
+Bayesian Neural Networks (BNNs) are a class of neural networks that estimate the uncertainty on their predictions via uncertainty
+on their weights. This is achieved by considering the weights of the neural network as random variables, and by learning their
+posterior distribution. This is in contrast to standard neural networks, which only learn a single set of weights, which can be
+seen as Dirac distributions on the weights.
+
+For more information on Bayesian Neural Networks, we refer the reader to the following resources:
+
+- Weight Uncertainty in Neural Networks `ICML2015 <https://arxiv.org/pdf/1505.05424.pdf>`_
+- Hands-on Bayesian Neural Networks - a Tutorial for Deep Learning Users `IEEE Computational Intelligence Magazine <https://arxiv.org/pdf/2007.06823.pdf>`_
+
+Training a Bayesian LeNet using TorchUncertainty models and Lightning
+---------------------------------------------------------------------
+
+In this part, we train a Bayesian LeNet, based on the model and routines already implemented in TU.
+
+1. Loading the utilities
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+To train a BNN using TorchUncertainty, we have to load the following modules:
+
+- our TUTrainer
+- the model: bayesian_lenet, which lies in the torch_uncertainty.model
+- the classification training routine from torch_uncertainty.routines
+- the Bayesian objective: the ELBOLoss, which lies in the torch_uncertainty.losses file
+- the datamodule that handles dataloaders: MNISTDataModule from torch_uncertainty.datamodules
+
+We will also need to define an optimizer using torch.optim and Pytorch's
+neural network utils from torch.nn.
+"""
+# %%
+from pathlib import Path
+
+from torch import nn, optim
+
+from torch_uncertainty import TUTrainer
+from torch_uncertainty.datamodules import MNISTDataModule
+from torch_uncertainty.losses import ELBOLoss
+from torch_uncertainty.models.lenet import bayesian_lenet
+from torch_uncertainty.routines import ClassificationRoutine
+
+# %%
+# 2. The Optimization Recipe
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~
+# We will use the Adam optimizer with the default learning rate of 0.001.
+
+
+def optim_lenet(model: nn.Module):
+    optimizer = optim.Adam(
+        model.parameters(),
+        lr=1e-3,
+    )
+    return optimizer
+
+
+# %%
+# 3. Creating the necessary variables
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+# In the following, we instantiate our trainer, define the root of the datasets and the logs.
+# We also create the datamodule that handles the MNIST dataset, dataloaders and transforms.
+# Please note that the datamodules can also handle OOD detection by setting the eval_ood
+# parameter to True. Finally, we create the model using the blueprint from torch_uncertainty.models.
+
+trainer = TUTrainer(accelerator="cpu", enable_progress_bar=False, max_epochs=1)
+
+# datamodule
+root = Path("data")
+datamodule = MNISTDataModule(root=root, batch_size=128, eval_ood=False)
+
+# model
+model = bayesian_lenet(datamodule.num_channels, datamodule.num_classes)
+
+# %%
+# 4. The Loss and the Training Routine
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# Then, we just have to define the loss to be used during training. To do this,
+# we redefine the default parameters from the ELBO loss using the partial
+# function from functools. We use the hyperparameters proposed in the blitz
+# library. As we are train a classification model, we use the CrossEntropyLoss
+# as the likelihood.
+# We then define the training routine using the classification training routine
+# from torch_uncertainty.classification. We provide the model, the ELBO
+# loss and the optimizer to the routine.
+
+loss = ELBOLoss(
+    model=model,
+    inner_loss=nn.CrossEntropyLoss(),
+    kl_weight=1 / 10000,
+    num_samples=3,
+)
+
+routine = ClassificationRoutine(
+    model=model,
+    num_classes=datamodule.num_classes,
+    loss=loss,
+    optim_recipe=optim_lenet(model),
+    is_ensemble=True
+)
+
+# %%
+# 5. Gathering Everything and Training the Model
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+# Now that we have prepared all of this, we just have to gather everything in
+# the main function and to train the model using our wrapper of Lightning Trainer.
+# Specifically, it needs the routine, that includes the model as well as the
+# training/eval logic and the datamodule
+# The dataset will be downloaded automatically in the root/data folder, and the
+# logs will be saved in the root/logs folder.
+
+trainer.fit(model=routine, datamodule=datamodule)
+trainer.test(model=routine, datamodule=datamodule)
+
+# %%
+# 6. Testing the Model
+# ~~~~~~~~~~~~~~~~~~~~
+#
+# Now that the model is trained, let's test it on MNIST.
+# Please note that we apply a reshape to the logits to determine the dimension corresponding to the ensemble
+# and to the batch. As for TorchUncertainty 0.2.0, the ensemble dimension is merged with the batch dimension
+# in this order (num_estimator x batch, classes).
+import matplotlib.pyplot as plt
+import numpy as np
+import torch
+import torchvision
+
+
+def imshow(img):
+    npimg = img.numpy()
+    plt.imshow(np.transpose(npimg, (1, 2, 0)))
+    plt.axis("off")
+    plt.tight_layout()
+    plt.show()
+
+
+dataiter = iter(datamodule.val_dataloader())
+images, labels = next(dataiter)
+
+# print images
+imshow(torchvision.utils.make_grid(images[:4, ...]))
+print("Ground truth: ", " ".join(f"{labels[j]}" for j in range(4)))
+
+# Put the model in eval mode to use several samples
+model = model.eval()
+logits = model(images).reshape(16, 128, 10) # num_estimators, batch_size, num_classes
+
+# We apply the softmax on the classes and average over the estimators
+probs = torch.nn.functional.softmax(logits, dim=-1)
+avg_probs = probs.mean(dim=0)
+var_probs = probs.std(dim=0)
+
+_, predicted = torch.max(avg_probs, 1)
+
+print("Predicted digits: ", " ".join(f"{predicted[j]}" for j in range(4)))
+print("Std. dev. of the scores over the posterior samples", " ".join(f"{var_probs[j][predicted[j]]:.3}" for j in range(4)))
+# %%
+# Here, we show the variance of the top prediction. This is a non-standard but intuitive way to show the diversity of the predictions
+# of the ensemble. Ideally, the variance should be high when the average top prediction is incorrect.
+#
+# References
+# ----------
+#
+# - **LeNet & MNIST:** LeCun, Y., Bottou, L., Bengio, Y., & Haffner, P. (1998). Gradient-based learning applied to document recognition. `Proceedings of the IEEE <http://vision.stanford.edu/cs598_spring07/papers/Lecun98.pdf>`_.
+# - **Bayesian Neural Networks:** Blundell, C., Cornebise, J., Kavukcuoglu, K., & Wierstra, D. (2015). Weight Uncertainty in Neural Networks. `ICML 2015 <https://arxiv.org/pdf/1505.05424.pdf>`_.
+# - **The Adam optimizer:** Kingma, D. P., & Ba, J. (2014). "Adam: A method for stochastic optimization." `ICLR 2015 <https://arxiv.org/pdf/1412.6980.pdf>`_.
+# - **The Blitz** `library <https://github.com/piEsposito/blitz-bayesian-deep-learning>`_ (for the hyperparameters).

auto_tutorials_source/Classification/tutorial_mc_batch_norm.py

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+"""
+Training a LeNet with Monte Carlo Batch Normalization
+=====================================================
+
+In this tutorial, we will train a LeNet classifier on the MNIST dataset using Monte-Carlo Batch Normalization (MCBN), a post-hoc Bayesian approximation method. 
+
+Training a LeNet with MCBN using TorchUncertainty models and PyTorch Lightning
+------------------------------------------------------------------------------
+In this part, we train a LeNet with batch normalization layers, based on the model and routines already implemented in TU.
+
+1. Loading the utilities
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+First, we have to load the following utilities from TorchUncertainty:
+
+- the TUTrainer from our framework
+- the datamodule handling dataloaders: MNISTDataModule from torch_uncertainty.datamodules
+- the model: LeNet, which lies in torch_uncertainty.models
+- the MC Batch Normalization wrapper: mc_batch_norm, which lies in torch_uncertainty.post_processing
+- the classification training routine in the torch_uncertainty.routines
+- an optimization recipe in the torch_uncertainty.optim_recipes module.
+
+We also need import the neural network utils within `torch.nn`.
+"""
+# %%
+from pathlib import Path
+
+from torch import nn
+
+from torch_uncertainty import TUTrainer
+from torch_uncertainty.datamodules import MNISTDataModule
+from torch_uncertainty.models.lenet import lenet
+from torch_uncertainty.optim_recipes import optim_cifar10_resnet18
+from torch_uncertainty.post_processing.mc_batch_norm import MCBatchNorm
+from torch_uncertainty.routines import ClassificationRoutine
+
+# %%
+# 2. Creating the necessary variables
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# In the following, we define the root of the datasets and the
+# logs. We also create the datamodule that handles the MNIST dataset
+# dataloaders and transforms.
+
+trainer = TUTrainer(accelerator="cpu", max_epochs=2, enable_progress_bar=False)
+
+# datamodule
+root = Path("data")
+datamodule = MNISTDataModule(root, batch_size=128)
+
+
+model = lenet(
+    in_channels=datamodule.num_channels,
+    num_classes=datamodule.num_classes,
+    norm=nn.BatchNorm2d,
+)
+
+# %%
+# 3. The Loss and the Training Routine
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# This is a classification problem, and we use CrossEntropyLoss as likelihood.
+# We define the training routine using the classification training routine from
+# torch_uncertainty.training.classification. We provide the number of classes,
+# and the optimization recipe.
+
+routine = ClassificationRoutine(
+    num_classes=datamodule.num_classes,
+    model=model,
+    loss=nn.CrossEntropyLoss(),
+    optim_recipe=optim_cifar10_resnet18(model),
+)
+
+# %%
+# 4. Gathering Everything and Training the Model
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# You can also save the results in a variable by saving the output of
+# `trainer.test`.
+
+trainer.fit(model=routine, datamodule=datamodule)
+perf = trainer.test(model=routine, datamodule=datamodule)
+
+# %%
+# 5. Wrapping the Model in a MCBatchNorm
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+# We can now wrap the model in a MCBatchNorm to add stochasticity to the
+# predictions. We specify that the BatchNorm layers are to be converted to
+# MCBatchNorm layers, and that we want to use 8 stochastic estimators.
+# The amount of stochasticity is controlled by the ``mc_batch_size`` argument.
+# The larger the ``mc_batch_size``, the more stochastic the predictions will be.
+# The authors suggest 32 as a good value for ``mc_batch_size`` but we use 4 here
+# to highlight the effect of stochasticity on the predictions.
+
+routine.model = MCBatchNorm(
+    routine.model, num_estimators=8, convert=True, mc_batch_size=16
+)
+routine.model.fit(datamodule.train)
+routine = routine.eval()  # To avoid prints
+
+# %%
+# 6. Testing the Model
+# ~~~~~~~~~~~~~~~~~~~~
+# Now that the model is trained, let's test it on MNIST. Don't forget to call
+# .eval() to enable Monte Carlo batch normalization at evaluation (sometimes called inference).
+# In this tutorial, we plot the most uncertain images, i.e. the images for which
+# the variance of the predictions is the highest.
+# Please note that we apply a reshape to the logits to determine the dimension corresponding to the ensemble
+# and to the batch. As for TorchUncertainty 2.0, the ensemble dimension is merged with the batch dimension
+# in this order (num_estimator x batch, classes).
+
+import matplotlib.pyplot as plt
+import numpy as np
+import torch
+import torchvision
+
+
+def imshow(img):
+    npimg = img.numpy()
+    plt.imshow(np.transpose(npimg, (1, 2, 0)))
+    plt.axis("off")
+    plt.tight_layout()
+    plt.show()
+
+
+dataiter = iter(datamodule.val_dataloader())
+images, labels = next(dataiter)
+
+routine.eval()
+logits = routine(images).reshape(8, 128, 10)  # num_estimators, batch_size, num_classes
+
+probs = torch.nn.functional.softmax(logits, dim=-1)
+most_uncertain = sorted(probs.var(0).sum(-1).topk(4).indices)
+
+# print images
+imshow(torchvision.utils.make_grid(images[most_uncertain, ...]))
+print("Ground truth: ", " ".join(f"{labels[j]}" for j in range(4)))
+
+for j in most_uncertain:
+    values, predicted = torch.max(probs[:, j], 1)
+    print(
+        f"Predicted digits for the image {j}: ",
+        " ".join([str(image_id.item()) for image_id in predicted]),
+    )
+
+# %%
+# The predictions are mostly erroneous, which is expected since we selected
+# the most uncertain images. We also see that there stochasticity in the
+# predictions, as the predictions for the same image differ depending on the
+# stochastic estimator used.