By data it hasn't seen before I mean a sample which doesn't exist in the training set. Maybe I'm not understanding something in the parent's argument.
For example, you train an image recognition model to tell cats and dogs apart using images from the internet, then you take out your phone, snap an image of your dog and give it to your algorithm to determine the species. When preprocessed this picture is equivalent to one row in a table with thousands of columns and this specific combination of pixel values doesn't exist anywhere else. Where is the hash function looking and for what in that case?
For example, you train an image recognition model to tell cats and dogs apart using images from the internet, then you take out your phone, snap an image of your dog and give it to your algorithm to determine the species. When preprocessed this picture is equivalent to one row in a table with thousands of columns and this specific combination of pixel values doesn't exist anywhere else. Where is the hash function looking and for what in that case?