Error functions, error signals, and conjugate gradient back propagation

We propose a three class taxonomy of error functions, based on the limit behaviour of the error signal. We classify four established error functions: the quadratic, Fahlman's Quickprop, entropy, and the exception error function. We introduce two new error functions, and benchmark all six on the N-2-N encoder. The two new functions found correct solutions faster and more reliably than the established functions.