question: Clarification on reload_dataloaders_every_epoch
context: I have a PyTorch Lightning DataModule instance that defines train_dataloader, val_dataloader, and test_dataloader.
  Currently using a custom callback to reload the train_dataloader that will resample the data.
  I saw that there is a Trainer flag called reload_dataloaders_every_epoch and soon to be reload_dataloaders_every_n_epochs.
  Do these just reload the train_dataloader, or do the do all 3?
answer: Only the train and validation dataloaders:
  
    
      
        pytorch-lightning/pytorch_lightning/trainer/training_loop.py
      
      
          Lines 168 to 170
        in
        e4f3a8d
      
    
    
      
  
          
            
             # reset train dataloader 
          
  
          
            
             if epoch != 0 and self.trainer.reload_dataloaders_every_epoch: 
          
  
          
            
                 self.trainer.reset_train_dataloader(model) 
          
      
    
  
  
  
    
      
        pytorch-lightning/pytorch_lightning/trainer/training_loop.py
      
      
          Lines 203 to 207
        in
        e4f3a8d
      
    
    
      
  
          
            
             if self.trainer.train_dataloader is None or not self.trainer.reload_dataloaders_every_epoch: 
          
  
          
            
                 self.trainer.reset_train_dataloader(model) 
          
  
          
            
              
          
  
          
            
             if self.trainer.val_dataloaders is None and not self.trainer.reload_dataloaders_every_epoch: 
          
  
          
            
                 self.trainer.reset_val_dataloader(model)