[andyjohnson0]

Thanks for taking the time to write such a comprehensive reply - much appreciated. "ML is maths" is something that I'm getting used to now. I do have some real uses in mind for what I'm learning' both in my job and some side projects, particularly image feature recognition, and I'm looking forward so seeing how it all works in out. Thanks again!

[bkanber]

Image feature recognition is not quite solved but I feel it's very close. It's easier, obviously, if the problem domain is very specific.

In the past, like when I started on ML, the best tip was to make sure to do some edge detection with a few convolutions before feeding an image to a neural network. Now, we have convolutional neural networks that kinda do that for you automatically.

Sometime in between those two dates, someone figured out how to get the convolutions trained via backpropagation -- and they did that by deriving the gradient of an arbitrary convolution (or more likely, looking it up). And that let us put convolutions right in the neural net and have the convolutions automatically train themselves along with the rest of the network. And we observe that the convolutions do things that we would do, like remove unnecessary detail and highlight edges or exaggerate colors.

Anyways; I believe the current state-of-the-art for generic image feature recognition is an ensemble of convolutional neural networks. I believe Google leads the pack on the commercial side so maybe look into how they do it.

[p1esk]

not quite solved is the right way to put it.

If you look at capsules papers, you will realize that convnets are not very good at recognizing transformations (e.g. 3d rotations) of the same object. That's probably why so many training examples are required to make them work well.

Also, if you look at errors made by state of the art models, some of them are obvious (to a human) objects, classified as something entirely different and unrelated. Which leads me to believe that object recognition is not completely solved until a model has some kind of common sense, either build in, or acquired during training.