Loss Function for Improved Learning with Noisy Labels

This repository contains an implementation of the loss function proposed in the paper "Combining Distance to Class Centroids and Outlier Discounting for Improved Learning with Noisy Labels". The loss function can be used to train deep neural networks, especially in the presence of noisy labels.

Usage

To use the loss function, follow these instructions:

Step 1:

Declare the following variables outside the class:

mean: The initialization mean for parameter u
std: The initialization standard deviation for parameter u
encoder_features: Number of features ϕ(xi) the output of the second to the last layer of our network
total_epochs: The total number of epochs the network is trained for

It is preferable to pass the above four variables using the config file. For simplicity, they have been declared global in this implementation.

Step 2:

Initialize the ncodLoss class with the following parameters:

labels: The list of training labels for all samples "should not be one hot encoded"
n: Total number of training samples
C: Total number of training classes

If you want to use the two additional regularization terms "the consistency regularizer LC and class-balance regularizer LB", pass the following parameters:

ratio_consistency The weightage given to LC. Check our paper for its value. Default is zero.
ratio_balance he weightage given to LB. Check our paper for its value. Default is zero.

Additional information for step 2:

self.beginning: It is turned to True because we start saving the average class latent representation from the beginning. Turn this to False at the time of saving the average latent representation of the class so that it will be turned on again by the function after the first run.

Step 3:

Call the forward method of ncodLoss with the following parameters:

index: The index of each training sample in the current batch.
f_x_i: The target output generated by the model (M).
y: one-hot encoded representation of each sample in the batch.
phi_x_i: encoded feature representation of each sample in a batch.
flag: The batch number or batch_id for each batch.
epoch: The number of the current epoch.

Note that in the case of the two-networked ensembles architecture, the size of outputs and out will be twice that of the number of indices because the second chunk contains the result of the augmented data of the first chunk.

Step 4:

Create an object of the above class ncodLoss and get the weights of u. Assign some learning rate to u (for learning rate check the paper) with zero weight decay and create a separate optimizer for u. We used SGD. Let us call it optimizer_u.

Step 5:

During training of the network, optimize the weights of u as well. For example:

  for current_epoch in total_number_of_epochs:
  
      for batch_number, (Actualdata, Augumented, label, indexs) in yourdataloader:
  
          Actualdata, label = Actualdata.to(device), label.long().to(device)
  
          y = torch.zeros(len(label),your_number_of_classes).to(device).scatter_(1, label.view(-1,1), 1)
  
          if (you want to use the additional regularisation of LC and LB) > 0:
              Augumented = Augumented.to(self.device)
              data = torch.cat([Actualdata, Augumented]).cuda()
          else:
              data = Actualdata
  
          f_x_i,phi_x_i = your_model(data)
  
          loss = object_of_ncodLoss(indexs, f_x_i, y, phi_x_i, batch_number, epoch)
  
          self.optimizer_u.zero_grad()
          self.your_own_optimizer.zero_grad()
  
          loss.backward()
  
          self.optimizer_u.step()
          self.your_own_optimizer.step()

Example:

For example, check the implementation folder

wanifarooq/NCOD