Thursday, 4 October 2012

Change in Neural Net Training Plans

After having spent the last few days training my NNs and seeing how long it is taking on my new data I have decided to change my training plans. I had been simultaneously training (on two separate computers) my decision tree idea alongside a more "normal" multi-class NN in the hope of eventually comparing the two. However, I anticipate that if I continued with this two pronged approach it would take about a month to finish, and I'd like quicker results than that. Also my attempt to use the hyperbolic tangent activation function hasn't been too successful and I'm not sure whether it's my coding or some deeper theoretical reason why it isn't working satisfactorily. Another reason is that the Coursera Neural Nets for Machine Learning course has just started, the syllabus for which is shown below:-

Lecture 1: Introduction
Lecture 2: The Perceptron learning procedure
Lecture 3: The backpropagation learning procedure
Lecture 4: Learning feature vectors for words
Lecture 5: Object recognition with neural nets
Lecture 6: Optimisation: How to make the learning go faster
Lecture 7: Recurrent neural networks and advanced optimisation
Lecture 8: How to make neural networks generalise better
Lecture 9: Combining multiple neural networks to improve generalisation
Deep Autoencoders (including semantic hashing and image search with binary codes)
Hopfield Nets and Simulated Annealing
Boltzmann machines and the general learning algorithm
Restricted Boltzmann machines and contrastive divergence learning
Applications of Restricted Boltzmann machines to collaborative filtering and document modelling.
Stacking restricted Boltzmann machines or shallow autoencoders to make deep nets.
The wake-sleep algorithm and its contrastive version
Recent applications of generatively pre-trained deep nets
Deep Boltzmann machines and how to pre-train them
Modelling hierarchical structure with neural nets

I think that rather than ploughing on with the training of my decision tree NN it would perhaps be better to finish this course before I get too carried away with myself with new NN ideas; for example, lecture 9, or the "stacking of Boltzman machines," might give me much better insight to the issues involved.

For these reasons I have decided to retrain my "reserve NN" on my enlarged data set with my new feature set, using both computers available to me, whilst I work through the above course. I expect that this reserve NN will be fully trained before the course ends, so then I will be free to experiment with my newly acquired knowledge.


Anonymous said...

How hard is the course compared to Andrew Ng's ? How strong is your math to handle this course?

Dekalog said...


Personally I found the Hinton course more difficult than Andrew Ng's, but if you've already done Ng's course the maths shouldn't be beyond your grasp. I would definitely recommend the Hinton course as a follow up to Prof. Ng's rather than the other way around!