A small pause in my series on the complexities of Deep Learning (or in general Machine Learning). Today I will try to give an honest review of the latest course I followed: “Convolutional Neural Networks” on Coursera by Andrew Ng.
I first followed the “Machine Learning” course from Andrew Ng in 2014. I really liked his pace of delivery and the way he builds up the knowledge to bring you up to speed. So, when his new nano degree on Deep Learning has been released in August of this year, I was one of the first to jump on it and I swiftly completed the three available courses. A couple of weeks back, the fourth out of five courses was released. I immediately went on the “Convolutional Neural Networks” course to continue my journey.
The course is well structured, as expected and given at a proper pace. The content is split on four weeks. The first week builds the foundations of Convolutional Neural Networks (CNN) and explains how those convolutions are computed, the mechanics. It explains its foundations in computer vision, then will detail the convolution with the padding, the stride and the pooling layers (max pooling, average pooling).
The second week looks at a few “classic” CNNs and explains how the architecture was built by adding new concepts on top of the previously existing ones. It then goes on explaining ResNets (a concept which can apply to other networks than only CNNs) and then build toward Inception Networks (yes, Inception as in the movie)
Third week introduces two new practical concepts, object localization and object detection. Figuring out where in a picture an object is, and secondly how many objects we can detect in a picture and where they each are. It nicely shows how bounding box predictions are made and evaluated followed by the use of Anchor boxes.
Finally, in the fourth week you will learn some of the coolest and funniest things about CNNs: face recognition and neural style transfer. Some important concepts introduced there are the one shot learning (another of those things which can apply to other networks than CNNs) and Siamese networks.
All in all, this is a good course. There are some glitches along the way. Some of the videos are not as polished as they could be i.e. some “bloopers” needs removal and a few errors which needs correction on the slides, but very minor. My biggest gripes is about the programming assignments. First, they are not self-contained. They right from the start refer to the introduction to Tensorflow made in the 3rd week of the second course of the nano degree: “Improving deep neural networks”. This makes things a little bit awkward when you do not use Tensorflow day to day (usually I’m fine with Keras) and there is 2–3 months in between the courses…
Second, the assignments are a bit less instructed than the other courses in the nano degree i.e. you will need to spend more time figuring out small bits of programming where not are not as much taken by the hand as in previous courses. This is not so much a problem as a statement, however it becomes a problem when combined with the problematic Coursera assignment submission engine (well, honestly, I do not know if it is Coursera fault or the course fault, but the result is the same). Sometimes it will refuse to correctly grade your assignment for things which are not even errors, or will introduce artificial boundaries without telling you those are there… I hope those get resolved soon, as it will not deter early adopters as myself, but will most probably discourage more than one in the future.
Lastly the jupyter kernels used on the site are troublesome. Server availability seems sketchy at times. You will often lose your work even if you saved it (you should save/export to your local machine regularly to alleviate those issues). In short, it is still a far way from the Kaggle kernels handling. The same issues have been reported by a colleague of mine following another Coursera course, so this is not unique to the CNN course. Also as the access to Coursera is now subscription based, you will lose access to your kernels if you do not renew your subscription after the course. Hence if you do not want to lose your work (as it is as much a reference as the course video themselves) you will have to store them locally on your machine or preferred cloud storage.
All that being said, it is an excellent course and taught me many things which I did not knew before, so an overall 4/5! But be ready for the glitches especially in the programming assignments. I especially enjoyed the one shot learning which I intend to apply to one of my deep neural network problem at work (not CNN related) and the neural style transfer. In that last programming exercise you complete the code of a neural style transfer algorithm. With a little push from my good friend Marc-Olivier, I went a little bit further and implemented a multi-style transfer algorithm. Here are my youngest kids with different level of style transfer from Edvard Munch, Pablo Picasso, Vincent Van Gogh and Georges Braque.
Originally published at medium.com/@TheLoneNut on November 22, 2017.