Validation loss averages loss across validation batches to provide a practical development signal. It is useful for monitoring training, but it is not a complete representation of model performance. section 9.1.2
Estimating validation loss
A loss-evaluation function switches the model to evaluation mode, samples ten batches from the validation split, averages their losses, and then restores training mode.
Use validation loss with deliberate interpretation:
- Treat the average as a convenient marker, not as a full description of how the model performs. section 9.1.2




