Keras and Learning Sine

One perspective on machine learning is that it is interpolation, curve fitting.

So I decided to try to fit sin(x) using a neural network.

Linear layers with Relu units will make piecewise linear curves.

It works, just not well.

Deep networks tend to get kind of hung up.

 

The final result is never all that great. Seems to have a lot of trouble at the minima and maxima of sine, probably because a relu is not a good model for what is happening at those points.  And it takes a lot of iterations for the rest to look pretty good. Perhaps the optimizer needs more fine tuning. I have not looked within the box much at all. Maybe a more aggressive optimizer would converge faster for this very simple task.

Here I plotted the result at intermediate steps of convergence. The accuracy tends to propagate out from 0 and sort of wrap around the curves. I wonder if this is due to where the thing is initialized

neural_progress

 

Still, I guess for being dead easy, not bad?

bad_maxima

 

 

 

Vomitting Out Some Machine Learning with Torch

Don’t know anything about Lua or Torch, and not so much about machine learning. Little project to get going.

Torch is to Lua what Numpy is to python. Never done any lua before, although for a while it was the main language on the esp8266. Torch seems like a popular base for machine learning in competition with theano and tensorflow. Lua is like if python and javascript has a slightly retarded baby.

Thought I’d give a simple tic tac toe playing guy a go. The structure is play a bunch of totally random games, collect up all the winning games. Then the problem is a classification problem where the categories are the next move (1-9).

Then used the stock nn neural network package to learn on it. Had a tough time finding clear docs. I am unimpressed.

Then use trained neural network to play against the random component.

The win stats increased from ~28% to ~45% (with some fluctuations run to run of a couple percent). Not bad. Especially since going second is disadvantageous. Okay, as I wrote that I realized it’s easy to try flipping that. Going first the stats go from 59% to 69%.

Hmmm. Maybe I should look at draws?

Also, a smart strategy for the moves would be to use the suggested moves according to their rank, not using the top suggested move then if that is invalid using a random move.