Examples: rhw-sequence.in

This is the sequence task introduced on page 358 of Parallel Distributed Processing, Explorations in the Microstructure of Cognition, Vol. 1, edited by David Rumelhart and James McClelland. The network used here is a pretty faithful reproduction of their network, based on the description provided.

This task is fairly difficult for a standard SRN. However, it sounds like Rumelhart, Hinton, and Williams were using simple recurrent backprop through time, which runs a single backprop pass that extends back in time from the end of the example to the beginning. Thus, an SRBPTT network was used here.

With the current settings, the network should learn the training set in about 400 sweeps, although it may be a bit unstable. Can you improve the speed with which the network learns? Hint: try Doug's Momentum with a learning rate around 0.1 and a weight randRange of 1.0.

How can you get better generalization out of the network? Should you use a lot of hidden units and weight decay or a few hidden units and try to encourage binary representations?

Try experimenting with the network's structure. It currently has a hidden layer that feeds back to itself and an output layer that feeds back to itself. Does the output feedback really help? What if you have the output feed back into the hidden layer like a Jordan net?

Douglas Rohde
Last modified: Fri Nov 17 12:50:00 EST 2000