Perceptron Learning
Perceptron learning is a gradient descent search
through the space of possible weights.
Each training example provides an "error surface"
for weights.  Learning rule runs weights downhill
with learning rate a as step size.
For linearly separable functions, there are no local
minima, and guaranteed to converge if learning
rate a not too high (overshoot)
Summary: Very effective for very simple
representable functions.