A source dataset is the original, usually larger dataset used to pretrain a model before adapting it to a related target task. Its learned weights provide a starting point that can reduce training time and labeled-data requirements. section 13.0 section 13.2.1
Transfer works best when the source and target datasets share useful structure. For image models, pretrained convolutional filters can detect broadly useful edges, colors, and image changes, while a new output layer matches the target classes. section 13.0 section 13.2.1
ImageNet to cats versus dogs
ResNet-18 pretrained on ImageNet uses ImageNet as its source dataset. Replacing its final fully connected layer with two outputs adapts the model to cat-versus-dog classification; the convolutional layers retain pretrained weights. section 13.2 section 13.2.1
Figure 13.5 The tradeoff between source and target dataset size and relevance. The top-right corner is the best place to be, and top-left is sub-optimal and won’t always work. The bottom half is a uniformly difficult place to do effective transfer learning.
Compare source-dataset size and relevance to the target dataset when judging whether transfer learning is likely to work well. section 13.2.1
