sreda, 24. avgust 2016

Beyond Backpropagation

Advances in Machine Learning Research

Gartner is predicting a very bright near future for the "Machine learning". 2015 was a peak year of inflated expectations, now, in 2016 is following period of disillusionment and in 2017 should be reached the plateau of productivity. Elsewhere this process usually last for 10 years. One kind of the most popular modern "machine learning" is named "Deep Learning" what is another name for neural networks with little bit more layers and perhaps even with a convolution and/or recursion. The learning of this kinds networks was until now usually based on gradient descent, on slow, iterative, non-reliable process named Backpropagation. That kind of learning is very demanding and extensive. On plain computer can last for hours or even many days and is often unsuccessful concluded. Recently are appeared two algorithms that significantly improve this kind of machine learning: "Bipropagation" and "Border pairs method".

Bipropagation algorithm is still iterative like a "backpropagation", but internal layers are not hidden anymore since their desired values are now calculated in advance before learning. That way can machine learning be conducted layer by layer, what represents great improvement (it could be more than a few ten times faster).

"Border pairs method" is a totally new algorithm which has many advantages over "backpropagation" algorithm. Firstly we look for the pairs of patterns of opposite class which are so near, that no third pattern does lie in between them. This are the Border pairs and only this patterns are significant when we want to draw a borderline between classes. So the majority of learning patterns (sometimes more than 90%) is eliminated even before the learning begins. Then we are trying to separate all border pairs with a minimal number of border lines, which represent neurons of the 1st layer, so we find the minimal structure of the neural network. While we draw one by one borderline, the learning of the first layer is done with only one neuron at the same time. Since these neurons have a hard limiter, they put binary output values and so the next layers could even be replaced with a logical circuit. Border pairs also allow a simple reduction of the noise.

More info 

So it is time for a change.